Immunology of Rheumatoid Diseases That Affect the Eye
MITCHELL H. FRIEDLAENDER
Table Of Contents
JUVENILE RHEUMATOID ARTHRITIS
SYSTEMIC LUPUS ERYTHEMATOSUS
GIANT CELL ARTERITIS
PROGRESSIVE SYSTEMIC SCLEROSIS (SCLERODERMA)
|Ocular disease is a characteristic feature of many rheumatologic disorders. Autoimmune mechanisms are believed to play a significant role in a number of these conditions, and a variety of immunologic abnormalities connected with rheumatoid disease already have been identified. Because the eye is only one of many organs affected, the immunologic abnormalities known to characterize the disease in other organs should throw light on the pathogenesis of the ocular lesions as well.|
|Ankylosing spondylitis is a chronic, progressive, inflammatory arthritis
that affects principally the sacroiliac joints and spine. About 25% of
cases are associated with an acute, recurrent iridocyclitis, often
bilateral, and accompanied by synechiae and glaucoma. Males are affected
with ankylosing spondylitis more often than females, accounting for 80% to 90% of
all patients. The disease occurs most frequently in the
second and third decades of life. Some 90% of patients have the histocompatibility
antigen HLA-B27. This represents the highest correlation
observed so far between an HLA type and a disease entity.|
The cause of ankylosing spondylitis is unknown. For many years, it was considered a variant of rheumatoid arthritis but is now known to differ in several important respects. There is no strong evidence of an autoimmune mechanism, and rheumatoid factor is negative except in approximately 5% of cases. It is well known, however, that genetic factors play a significant role. The disease is 40 times more common among first-degree relatives than in the general population, and the concordance rate in affected identical twins is 70%.1 Family pedigrees suggest that the gene for ankylosing spondylitis is inherited as a Mendelian dominant trait with 70% penetrance in males and 10% in females.2 It also is known that the frequency of ankylosing spondylitis is high among certain American Indian groups such as the Haida, Bella Coola, and Pima and relatively rare among blacks.3,4
Histocompatibility (HLA) antigens are cell surface determinants present on most human cell membranes. Their specificity in humans is governed by a group of genes located on the sixth chromosome. Each gene determines a cell surface antigen so that an individual will have four cell surface antigens that are determined genetically. The frequency of an HLA type can be determined by testing a patient's lymphocytes with a number of different antisera.
Although HLA typing has been used principally to match donors and recipients in organ transplantation, the association of HLA types with specific disease entities is now receiving considerable attention. In 1973, Schlosstein and his colleagues5 in Los Angeles and Brewerton and his colleagues6 in England reported a strikingly high incidence of HLA-B27 in patients with spondylitis. They found the antigen (which has a frequency of 4% to 9% in control populations) in 95% of patients with ankylosing spondylitis, and comparably high percentages have been reported by other investigators.
Ankylosing spondylitis is common in families that propagate the HLA-B27 antigen. It has been estimated that if the risk that an antigen-negative female will have spondylitis is one, then the risk in a B27-positive female is 276 times greater. For a B27-positive male, the risk is 1937 times greater.
The significance of this high frequency of HLA-B27 in patients affected with ankylosing spondylitis is uncertain. The antigen also is found in 90% of patients with a spondylitis that occurs after infection with Yersinia enterocolitica. This is a gram-negative bacterium that causes a transient inflammatory bowel disorder that is sometimes followed by polyarthritis and sacroiliitis. In patients who recover uneventfully from the infection, the incidence of HLA-B27 is the same as for the general population, but of those in whom arthritis develops, B27 is found in approximately 90%. This suggests that spondylitis can follow an infectious disease in a genetically susceptible individual. Whether this is because of a defective immune response or a hypersensitivity mechanism is not known. An infectious disease process also may be the basis of Reiter's syndrome and even of ankylosing spondylitis.
|Reiter's syndrome consists of a triad of lesions—acute conjunctivitis, nonspecific
urethritis, and arthritis—with punctate keratitis, corneal
stromal opacities, and iritis, sometimes also in evidence. The
disease usually occurs in sexually active males and often follows
dysenteric infections with Shigella, Yersinia, or Salmonella.|
As with ankylosing spondylitis, most patients with Reiter's syndrome (90%) have the histocompatibility antigen HLA-B27. The reason for this association is not known. The first possibility is that the B27 antigen may act as a favorable receptor site for certain microbial pathogens, a number of which, especially Chlamydia, Mycoplasma, and Shigella, have been irregularly associated with Reiter's syndrome. A second possibility is that infectious agents that cause Reiter's syndrome and other rheumatoid diseases share common antigens with the host's own connective tissues. This could result in the host's inability to recognize and combat the invading microbe, or alternatively it could result in an immume response directed against the host's tissues as well as against the infectious agent. A third possibility, and the most widely accepted, is that HLA-B27 is linked in the genetic material to an immune-response gene and that this gene is responsible for the clinical syndrome. The immune response may be directed appropriately against the infecting agent or inappropriately against the patient's own tissues.
There are only a few immunologic abnormalities in patients with Reiter's syndrome. Cellular immunity is intact, although lymphocyte transformation has been shown with chlamydial and prostatic antigens.7 In some patients with Reiter's syndrome, cell-mediated immunity to autologous immunoglobulin G (IgG) also has been found.8
In one of many attempts that have been made to implicate a microorganism in Reiter's syndrome, Schachter and associates9 propagated a chlamydial agent that they had isolated from synovial fluid, synovial membranes, urethras, and conjunctival of patients with the syndrome. When they recovered the organism from the synovial membrane of an affected patient and inoculated it into the anterior chambers of rabbits, ocular disease (consisting of papillary conjunctivitis, corneal edema, corneal opacities, corneal neovascularization, and iritis) developed.10 Several cases of Reiter's syndrome also have been reported in association with Shigella dysentery and other enteric infections, and it may be that a number of infectious agents can produce the syndrome in genetically susceptible individuals.11
|Rheumatoid arthritis is a chronic, recurrent, systemic inflammation that
affects mainly the peripheral joints. It occurs in 2% or 3% of the population, is
three times more frequent in females than in males, and
usually appears between the ages of 30 and 50 years. Constitutional symptoms
may include malaise, fever, and weight loss. The peripheral joints
on both sides of the body are affected first, and the arthritis usually
progresses centripetally. Scleritis is a frequent and important
complication, and the cornea and uveal tract may be affected secondarily. There
is no consistent pattern of inheritance in rheumatoid arthritis
and no known prevalence of any HLA antigen.|
The antigenic stimulus that initiates joint inflammation in rheumatoid arthritis still is a mystery. Certain microorganisms have been implicated, but their causal roles still are uncertain. Viruses, particularly the slow viruses, may play a role, although no virus particles have been certainly identified. The results of attempts to isolate Mycoplasma and rubella virus from the joints of patients with rheumatoid arthritis have been inconclusive.12 During the prodromal stage of hepatitis, hepatitis B virus can form immune complexes and produce a syndrome resembling serum sickness with polyarthralgia and vasculitis. This virus seems to be the first virus known to produce a chronic rheumatic disorder in humans, and, like many other infectious agents, it can give rise to rheumatoid factor in serum. The clinical syndrome, however, bears no resemblance to either rheumatoid arthritis or systemic lupus erythematosus (SLE).
Other possible infectious causes of rheumatoid arthritis have been investigated. Rheumatoid synovial cells show a diminished sensitivity to infection with either Newcastle disease virus or rubella virus. Mycoplasma antibodies have been isolated from patients with rheumatoid arthritis, especially from those with longstanding disease, and recently a slow-growing infectious agent with some of the properties of Mycoplasma has been isolated from the synovial fluid of such patients.13 In other studies, however, investigators have failed to find any evidence of previous Mycoplasma infection in patients with rheumatoid arthritis.14
A variety of immunologic abnormalities have been found in patients with rheumatoid arthritis, and there now is considerable evidence that the disease is caused by an autoimmune process. Antibodies against IgG are formed in the patient's blood and synovial fluid. Immune complexes that are formed and deposited in the joints and other tissues activate the complement system through the classic and alternate pathways.15 Activation of the complement system results in a number of inflammatory phenomena, including chemotaxis of leukocytes, histamine release, and cell lysis. Enzymes released by the synovial leukocytes produce inflammatory changes in the joints and the destruction of normal structures. The inflammatory response is amplified by the various Immoral amplification systems.
The Immoral immune system appears to be highly active and important in the pathogenesis of rheumatoid arthritis (Fig. 1). The number of synovial B lymphocytes, which are precursors of antibody-producing plasma cells, often is abnormally high. More than 50% of the synovial plasma cells produce IgG rheumatoid factor, an antibody directed against other IgG molecules.10 Immune complexes may be found within plasma cells of the synovial membrane, a finding unparalleled in any other immunopathologic disorder. Although a greater-than-normal number of peripheral B cells usually are found, the number is hard to estimate because of the antilymphocyte antibodies present.16 When these antibodies are removed, the number of peripheral B cells may in fact be reduced.
The following antibodies also have been identified in the sera of patients with rheumatoid arthritis: (1) antibodies to double-stranded DNA; (2) antibodies to human native and denatured collagen; and (3) antinuclear antibodies (ANAs).17,18 Recently, it has been shown that IgG molecules in the sera of patients with rheumatoid arthritis have a conformational anomaly in the hinge region.19 This altered IgG may be recognized as abnormal by B-lymphocyte receptors, leading to an Immoral autoimmune response directed against IgG.
The following defects in cellular immunity also have been associated with rheumatoid arthritis:
This T-cell response to IgG antigens and the fact that soluble mediators of lymphocytes contribute to the inflammatory changes that take place in the rheumatoid joint strongly suggest that there is a cell-mediated immune component in rheumatoid arthritis.
A third population of lymphocytes, lacking conventional B- and T-cell markers, may be important in the pathogenesis of rheumatoid disease. This population, known as “null cells,” may include the so-called killer lymphocytes (K cells) that are cytotoxic to IgG-coated target cells.22 Null cells may be responsible for the formation of “rheumatoid rosettes,” which are formed by the interaction of lymphocytes and IgG-coated indicator erythrocytes. In addition, peripheral blood leukocytes collected from patients with rheumatoid arthritis may be cytotoxic for synovial cells.23
Antigen preparations of uvea-retina, synovial membrane, and articular cartilage inhibit the migration of leukocytes obtained from patients with rheumatoid arthritis.24 In ankylosing spondylitis, inhibition is induced only by synovial membrane antigens. Lymphocytes from blood and synovial fluid of patients with rheumatoid arthritis also show a markedly diminished blastogenic response to phytohemagglutinin and pokeweed mitogen.25
The reason for depressed cellular immunity in rheumatoid arthritis is unknown. It may result from a preoccupation of the host's immune mechanism with cell-mediated immune reactions related to the pathogenesis of the disease, or it may be related to a systemic viral infection. Alternatively, depressed cellular immunity may be caused by immune complex formation or by rheumatoid arthritis therapy. The HLA-Dw4 allele occurs with high frequency and DQw7 influences severity.26
|JUVENILE RHEUMATOID ARTHRITIS|
|Juvenile rheumatoid arthritis (JRA) is a major chronic, progressive, crippling
disease of childhood. It has a peak incidence between the ages
of 2 and 4 years and a lesser peak between the ages of 10 and 12 years. It
occurs twice as often in females as in males and has an average
duration of approximately 6½ years. A major complication of JRA
is chronic iridocyclitis, and cataract formation and band keratopathy
also may occur. The ocular disease is one of the leading causes of uveitis
in childhood and may be associated with significant visual disability. JRA
is conveniently divided into three forms: (1) the acute, toxic
form (Still's disease); (2) a polyarticular form; and (3) a pauciarticular
form. Patients with this third form have the highest incidence
Although rheumatoid factor is prevalent in adult rheumatoid arthritis, it is not commonly found in patients with JRA, with only 10% to 20% testing positively compared with 50% to 85% of those with the adult disease. Conversely, ANAs are found in 20% to 40% of children with JRA (most with pauciarticular and polyarticular JRA but a few with Still's disease) and in 88% of JRA patients who have chronic iridocyclitis.27,28 The ANAs are predominantly of the IgG immunoglobulin class and the titers are 1:50 or higher in most patients. The consistent homogeneity of the nuclear fluorescence pattern is typical of reactivity against deoxyribonucleoprotein.29 Antibodies to DNA and RNA usually are not demonstrable, but antibodies against double-stranded RNA recently have been reported in children with JRA and iridocyclitis.30 A positive ANA test result usually precedes the onset of iridocyclitis and may be useful in identifying patients with JRA who are likely to have chronic iridocyclitis develop. The reason for a positive ANA test result in this disease is not known, but in general both infectious processes and host immune defects are associated with the formation of ANA and other autoantibodies.
In patients with JRA and iridocyclitis, smooth-muscle antibodies, usually of the immunoglobulin M (IgM) class, are found in 15% to 23%, which is the same frequency with which they are found in control groups. The HLA antigens of patients with JRA have been examined, and some investigators have reported a high incidence of HLA-B27.31,32 Others have not found this to be the case, however, and suggest that the earlier studies included patients with ankylosing spondylitis, which, in its early stages, can mimic JRA.33,34
The clinical picture of Still's disease suggests the possibility of a disseminated infection. Evidence indicating an infectious etiology is scant, however. A rise in antibody titer to Coxsackie B3 and A9 viruses and the isolation of adenovirus 7 have both been reported.29 The titer of rubella virus antibody has been found to be elevated, and rubella virus antigen has been isolated from synovial fluid. Perhaps a viral infection, combined with defective immunity, allows an infectious agent to persist in eye and joint tissues, which leads to the development of JRA.
|SYSTEMIC LUPUS ERYTHEMATOSUS|
|Systemic lupus erythematosus is a multisystem collagen-vascular disease. The
etiology is unknown, but hereditary, immunologic, and microbiologic
factors seem to be concerned. SLE is characterized by a tendency to
form autoantibodies, especially to constituents of the cell nucleus. The
main organ systems affected are the joints, skin (including the skin
of the eyelids), kidneys, lungs, and heart. The eye and central nervous
system also may be affected. Cotton-wool spots and retinal vasculitis
may occur and sometimes scleritis, corneal opacities, and optic
neuritis. SLE is seen most commonly in women of the child-bearing age
and more commonly in nonwhites than in whites.|
Recent investigations have shown that genetic susceptibility, possible viral infection, and abnormal immune responses interact in the pathogenesis of SLE. Antibody formation to double-stranded DNA occurs frequently and is associated with disease activity. Depressed T-cell activity, enhanced B-cell activity, and a low level of serum complement also are prominent features of the disease.
Much of our current understanding of SLE is derived from animal studies in which an animal model of the disease in New Zealand black (NZB) mice was used. NZB mice have a deficiency of suppressor T cells and a related low level of a circulating thymic hormone known as thymosin. They are immunologically impaired and susceptible to various infections, including those caused by oncogenic viruses. Both NZB mice and hybrid NZBNZW (New Zealand white) mice have been studied extensively. NZB mice, hybrid mice, and humans with SLE have ANAs in their blood and deposits of both immune complexes and components of the complement system in their kidneys.
These immune complexes contain DNA and antibodies against DNA, but the source of the DNA is not known. It could be released from damaged cells (possibly as a result of viral infection) or it could itself be of viral origin. Viruses have been implicated in the development of both human SLE and the mouse disease. Type C virus has been identified in NZB mice and can be transmitted genetically from parent to progeny in the egg and sperm. Copies of the viral genome can thus be incorporated into the cellular genome. It has been suggested that a genetic defect in NZB mice permits expression of the viral genome and that this, in turn, results in autoimmune disease. The pathologic changes might be caused by the development of antibodies against viral components, with the antibodies forming immune complexes with the viral antigen and being deposited in the kidneys and other organs. A second possibility is that viral antigens on cell surfaces provoke an immunologic attack on these infected cells, which are not recognized by the host as “self.” Antigens related to those of type C virus also have been identified on the lymphocytes and in the kidneys of some patients with SLE. Fifty to 60% of patients have antibodies to cardiolipin.35 This antibody may be associated with occlusive retinal vasculitis.
Currently, the most popular conception of the pathogenesis of SLE is as follows: The infectious agent is a type C RNA virus, which is known to be transmitted genetically in animals. Because of a genetic predisposition of the host, the virus avoids the immune surveillance system and homes in on, replicates, or is recognized in the thymus. The thymic alteration may eventually destroy T-cell function, either directly or by way of an autoimmune mechanism. Further viral replication and dissemination are permitted because of a defect in cellular immunity, and this leads to an escalated humoral immune response. Immune complexes are formed, circulated, and deposited in various organs, producing inflammatory reactions and activation of the complement system. Inflammation and clinical disease then develop.
Studies of lymphocytes from patients with SLE indicate that when the disease is active, the T cells are markedly reduced, the null cells are increased, and the B cells usually remain at their normal level. T-cell lymphopenia may be caused by the increased number of null cells. (The null cells, which mature on exposure to thymus, may simply be immature T cells. If this is the case, the population of T cells would increase as the null cells mature.)
Monocyte-macrophage function is depressed in early SLE, and since these cells participate in the processing of antigen and in lymphokine activity, this defect could result in depressed cellular immunity.36 A lupus-like syndrome has been associated with deficiency of the second component of complement (C2), and it may be that an inherited deficiency of this component could predispose an individual to lupus or to faulty handling of viral infections.37
Histocompatibility antigens have been investigated in both SLE and discoid lupus erythematosus (DLE), a cutaneous variant of SLE. Female patients with SLE show a significant association with HLA-B8, and patients with DLE have a greater-than-normal association with both HLA-B7 and HLA-B8.38
|Sjögren's syndrome is a chronic inflammatory disease of unknown
origin that primarily affects the lacrimal and salivary glands. Its
clinical hallmark is dryness of the oral mucosa, conjunctive, and other
mucous membranes. Half of the patients with Sjögren's syndrome
have rheumatoid arthritis, and a smaller group have other connective
tissue diseases. A presumptive diagnosis of Sjögren's syndrome
can be made if two of the following three features are present: (1) recurrent
or chronic idiopathic swelling of the salivary glands; (2) unexplained
xerostomia; and (3) connective tissue disease. A definitive
diagnosis can be made if there is objective evidence of keratoconjunctivitis
sicca or a typical histopathologic change in the lacrimal
or salivary glands.|
Sjögren's syndrome is characterized by the development of lymphocytic infiltrates and by destruction of the salivary and lacrimal glands and other tissues. Both T and B lymphocytes have been detected in the salivary gland infiltrates.39 Examination of the peripheral blood usually shows a modest increase in the peripheral B lymphocytes, and the T lymphocytes are reduced in approximately one-third of patients. The lymphocytes infiltrating the salivary glands synthesize IgM and IgG (locally), rheumatoid factor, and other autoantibodies.
Hypergammaglobulinemia, usually of the polyclonal type, is the most frequent immunopathologic finding in Sjögren's syndrome. Rheumatoid factor is found in at least 75% of patients, and the titers are especially high in those with the sicca complex (keratoconjunctivitis sicca and xerostomia alone). ANAs occur in approximately 90% of patients, and the staining pattern usually is homogeneous or speckled.40 Antidouble-stranded DNA antibodies and lupus erythematosus (LE) cells are found in a small percentage of patients, and autoantibodies against salivary-duct antigens may be detected in approximately 50% of patients.
Whereas humoral antibody formation in Sjögren's syndrome is exuberant, cellular immunity appears to be somewhat depressed. Patients with the disease do not have delayed hypersensitivity to contact allergens develop, and peripheral blood lymphocytes do not respond normally to mitogens.41 Cellular hypersensitivity to salivary gland extract has been demonstrated by the use of peripheral blood leukocytes from affected patients. Perhaps T-lymphocyte sensitization to salivary gland antigens (with the production of lymphokines) occurs and is responsible for pathologic changes. As in other autoimmune disorders, there probably is a defect in T-suppressor cells in Sjögren's syndrome. Such a deficiency could permit the uncontrolled proliferation of B cells and the development of overactive immune responses such as autoantibody formation. Antibodies to Epstein-Barr virus have been detected in the blood and saliva of patients with Sjögren's syndrome.42
Patients with Sjögren's syndrome are predisposed to such lymphoproliferative disorders as lymphoma, leukemia, and Waldenstrom's macroglobulinemia.43 An intermediate stage of lymphoproliferation, known as “pseudolymphoma,” also may occur. Whether Sjögren's syndrome is the result of a slow or latent viral disease or a disorder of immunologic regulation remains to be determined. Androgens and prolactin may play a role in regulating the lacrimal gland.44
|Polyarteritis nodosa (once known as periarteritis nodosa) is a connective
tissue disorder and one of a number of arteritis-vasculitis syndromes; its
hallmark is widespread inflammation of medium and small-sized
arteries. Nearly any organ can be affected, and there are ocular manifestations—scleritis, sclerokeratitis, uveitis, retinal vasculitis, and
optic neuritis—in 10% to 20% of patients. A number of factors
suggest that the disease is immunologic in nature and probably mediated
by immune complex deposition within vessels. Other clinical entities
that can be considered arteritis-vasculitis syndromes are hypersensitivity
angiitis, temporal arteritis, vasculitis associated with rheumatic
fever, and allergic granulomatous angiitis. The pathogenesis of
these syndromes (which were classified by Zeek45 and then more fully by Hawkins46 [Table 1]) is thought to be similar to that of polyarteritis nodosa.|
Vasculitis Associated With Connective Tissue Diseases
Vasculitis Associated With Rheumatic Fever
Vasculitis With a Granulomatous Component
Allergic granulomatous angiitis (Churg and Strauss)
Other Vasculitides and Disorders Associated with Vasculitis
(Adapted from Zeek PM: Am J Clin Pathol 22:777, 1952.)
Although most cases of polyarteritis nodosa appear to be related to hypersensitivity, the antigen (or antigens) has not been identified. However, humoral factors play a role. This is indicated by the following:
In human cases, immune complexes have been deposited in vessel walls during active disease. The work of Gocke and associates47 has shown that circulating immune complexes composed of Australia antigen and immunoglobulin are present in the sera of patients in whom polyarteritis nodosa has been established by biopsy. Some of these patients also show deposition of Australia antigen, IgM, and complement in blood vessel walls (Fig. 2). Although this intriguing finding suggests a relationship between polyarteritis nodosa and exposure to a microorganism, most cases do not have circulating immune complexes containing Australia antigen.
Renal biopsy specimens from patients with the disease have shown deposition of such immune reactants as immunoglobulins, complement, and fibrin. Such deposition has not been found consistently, however, and may in fact be nonspecific.
Microbial antigens, drugs, and autoantigens may play a role in widespread vascular inflammation. Streptococcal antigens and numerous drugs—sulfonamides, penicillin, diphenylhydantoin, arsenical, thiouracil, iodides, and thiazides—have been associated with polyarteritis, hypersensitivity angiitis, and Henoch-Schonlein purpura. There also is a high association between methamphetamine abuse and polyarteritis nodosa. The fact that many such drug users eventually have hepatitis develop strengthens the evidence that there is an association between polyarteritis nodosa and Australia antigen.
Histologically, the typical lesion of polyarteritis nodosa is an infiltration of neutrophils and eosinophils around medium and small arteries. The necrotizing, inflammatory process is located most commonly at blood-vessel bifurcation sites. Round-cell infiltration occurs in the chronic phase of inflammation and is followed ultimately by fibrinoid necrosis.
|Wegener's granulomatosis usually is described as a triad of lesions: (1) necrotizing
granulomas of the respiratory tract; (2) disseminated
vasculitis of the small and medium-sized arteries and veins; and (3) glomerulonephritis. It
affects mainly young and middle-aged individuals, and
ocular lesions—orbital and nasolacrimal granulomas, peripheral
corneal degeneration, scleritis, and retinal vasculitis—frequently
occur. A limited form of the disease has been described in
which the pulmonary lesions are typical, but lesions elsewhere are limited
or absent. Midline granuloma is sometimes classified as a manifestation
of Wegener's granulomatosis, but the validity of such a classification
has been seriously questioned.|
Wegener's granulomatosis is a necrotizing vasculitis with the features of an autoimmune disorder. Circulating autoantibodies to smooth muscle, circulating immune complexes, and reduced levels of serum complement have all been found. Complement and immunoglobulins have been detected in the vascular lesions of the skin and kidneys.48 IgG and C3 were found in the glomeruli of one patient, suggesting an immune complex deposition, and IgG, C3, and fibrin were found in the glomerular vessels of another patient.49,50 Elevated levels of serum IgA, IgE, and C3 also have been reported.51 Subepithelial basement-membrane deposition of IgG and complement has been found in the glomerular tufts in a lumpy-bumpy pattern characteristic of immune complex disease.
The level of delayed skin hypersensitivity to various common skin-test antigens is abnormally low in Wegener's granulomatosis. Reduced lymphocyte mitogenic responses also have been documented, but some of the studies were performed on patients treated with immunosuppressive agents.
|GIANT CELL ARTERITIS|
|Giant cell arteritis is a term used to describe a group of vasculitides in which epithelioid
or giant cells infiltrate the walls of vessels. The principal diseases
are temporal arteritis, polymyalgia rheumatica, and aortic-arch syndrome
or Takayasu's disease, with temporal arteritis the most important
to the ophthalmologist. Because of the ischemic optic neuritis
and the central retinal-artery occlusion that sometimes accompany the
disease, temporal arteritis ranks as one of the prime medical emergencies
in ophthalmology. Rapid recognition and prompt treatment are essential
for the preservation of vision in affected patients.|
The hallmark of temporal arteritis is granulomatous inflammation that affects the temporal arteries selectively.52 The presence of epithelioid or giant cells is characteristic. Destruction of the internal elastic lamina is common but not diagnostic. The best way to confirm the diagnosis is with a temporal artery biopsy. But although it has been stated that a pattern of inflammation characteristic of temporal arteritis can always be found in any such biopsy specimen, according to other observers, “skip areas” make it possible for an entire biopsy specimen to lack the tell-tale evidence.52,53
Immunofluorescent studies have shown deposition of IgG, IgA, IgM, and complement in the cytoplasm of cells and in the elastic tissue within vessel walls.54 ANA directed against nuclei of cells within vessel walls may be seen in patients who have serum ANA. A nonspecific elevation of the levels of alpha-2 globulin and fibrinogen in plasma also has been noted. Because these proteins reduce the electronegative charge on circulating erythrocytes and promote rouleaux formation, their elevation may account for the high erythrocyte sedimentation rate in patients with giant cell arteritis.55 Immunoglobulin abnormalities usually are not observed, but elevated levels of IgM have been noted in a number of patients.55 Lymphocytes from patients with polymyalgia rheumatica undergo blast transformation in vitro in the presence of either arterial antigens or homogenates of whole muscle contaminated with vascular antigens.54,56
There has been some recent speculation that viral antigens may participate in giant cell arteritis and polymyalgia rheumatica. Cytoplasmic inclusion bodies recently have been found in temporal artery biopsy specimens.57 The meningoencephalitis caused by varicella virus has been reported as having histologic features similar to those of giant cell arteritis, and others have found the vessels of the central nervous system selectively affected by varicella virus.57,58 Segmental artery involvement also has been reported shortly after an attack of herpes zoster ophthalmicus.59 Perhaps viruses or other infectious agents can alter vascular antigens and produce an autoallergic inflammation.
Takayasu's disease is associated with an elevation of serum IgG, IgA, and IgM.60 Perhaps there also is a fundamental immunologic abnormality in this disease.
|Polymyositis and dermatomyositis
encompass a spectrum of related disorders characterized by inflammation
and degeneration of varying amounts of skeletal muscle. They are multisystem
diseases with the features of rheumatic disorders and may occur in association
with malignancy. Ocular manifestations rarely are reported but do occur.
The most common are a heliotrope rash affecting the eyelids, iritis, conjunctivitis,
episcleritis, cotton-wool spots, retinal hemorrhages, and extraocular muscle
palsies. Five categories of polymyositis-dermatomyositis have been recognized:
(1) idiopathic polymyositis; (2) idiopathic dermatomyositis; (3) polymyositis-dermatomyositis
associated with malignancy; (4) childhood polymyositis-dermatomyositis;
and (5) polymyositis-dermatomyositis associated with other rheumatoid diseases.
The etiology of these disorders currently is unknown. Features of both humoral and cellular immunity have been recognized in affected patients, and there has been speculation that a virus may play an etiologic role.
Circulating antibodies to muscle can be found after any muscle injury. Local deposits of IgG, IgM, and complement have been found within the vessel walls of affected skin and muscle in polymyositis.61 These deposits, detectable mainly in children with diffuse vasculitis, suggest the possibility of an immune complex disorder. Polyclonal hypergammaglobulinemia often is seen in patients with polymyositis-dermatomyositis, and both rheumatoid factor and ANA are demonstrable in 20% of cases. Because patients with agammaglobulinemia can have polymyositis develop, immunoglobulins are clearly not a requirement.62 Dermatomyositis has been reported in association with C2 deficiency, indicating further that the classic pathway of complement activation is not always required.63 Deficiencies of the complement system have been reported in association with a number of rheumatic abnormalities, suggesting that patients with rheumatic disease are abnormally susceptible to immunologic injury.
There is evidence that cellular immunity participates in the development of polymyositis-dermatomyositis. Lymphocytes from patients with active myositis induce cytotoxic changes in autologous or chick muscle cells in tissue culture.64 Muscle cell injury is thought to be caused by lymphotoxin, a lymphokine produced by T cells. The lymphocytes from affected patients sometimes respond to their own muscle antigens as though they were foreign (Fig. 3). This could be because of an altered membrane antigen on the muscle cells, induced perhaps by a virus. Alternatively, there may be a primary defect in antigen recognition by lymphocytes or a cross-reactivity between muscle antigen and an unidentified foreign antigen. Presumably, the cellular response would occur at the site of the instigating antigen, and lymphotoxin could diffuse through the tissues and injure the remote muscle fibers.
Electron microscopy has identified virus-like particles of various structural types in the myocytes of patients with polymyositis. Although the etiology of these disorders remains speculative, a combination of viral and immunologic abnormalities is suggested by current available evidence. Histologic findings show an infiltration of muscle cells with a focal or diffuse lymphocytic infiltrate. Necrosis, degeneration, and regeneration of muscle cells are typical.
|PROGRESSIVE SYSTEMIC SCLEROSIS (SCLERODERMA)|
|Progressive systemic sclerosis is a connective tissue disease affecting
various organ systems, especially the skin, lungs, and gastrointestinal
tract. For many years, it was considered primarily a dermatologic condition, but
its systemic nature is now well recognized. The main pathologic
feature is a greater-than-normal collagen deposition in the affected
organs. The rare ocular findings cover a spectrum of abnormalities
that include brawny edema of the eyelids, keratoconjunctivitis sicca, cotton-wool
spots, retinal hemorrhage, disc edema, and uveitis.|
The etiology of progressive systemic sclerosis is unknown, but the following three pathogenic mechanisms may possibly contribute to the development of the disease: (1) an immunologic defect, (2) an autonomic nervous system defect, and (3) a primary connective tissue defect.
Several immunologic abnormalities have been detected in affected patients. Most patients have a hypergammaglobulinemia of the polyclonal type, and rheumatoid factor is found in approximately 35% of patients. Test results for lupus erythematosus cells occasionally are positive, and serologic test results for syphilis are falsely positive. ANAs, usually of the coarse, speckled, nuclear type, are present in at least 60% of patients but do not correlate with the clinical severity of the disease.65
Antinucleolar antibodies and antibodies to ribonucleoprotein also are found, and one investigating team recently found a new ANA marker system by using a concentrated tissue extract as antigen.66 This new antibody seems to be specific for the disease, since it is not found in other connective tissue disorders.
A mixed cryoglobulin containing IgG and IgM and usually associated with antigammaglobulin activity in serum has been found in 50% of patients with progressive systemic sclerosis.62 Although this suggests the possibility of circulating immune complexes, their role (if they exist) and the etiology of the disease remain uncertain. There still is relatively little evidence that the associated vascular abnormalities are based on a humoral immunologic defect.
There also is some evidence that cellular immune mechanisms participate in progressive systemic sclerosis. Lymphocytes from patients with the disease can destroy embryonic fibroblasts in tissue culture. Cellular infiltration of affected tissue is slight, however, except in the synovium.
The importance of a component of the autonomic nervous system in progressive systemic sclerosis has been emphasized.67 The high incidence of both Raynaud's phenomenon and esophageal abnormalities, their reversal by reserpine and methacholine, and their impaired responses to gastrin I and edrophonium all suggest an autonomic abnormality. To be effective, the latter two drugs (gastrin I and edrophonium) require an intact autonomic nervous system.
A primary defect in collagen has been suggested as contributing to progressive systemic sclerosis. Collagen biosynthesis is elevated in tissue culture, and there are abnormalities in the conversion of proline to hydroxyproline.68,69
By microscopic examination, sclerosis and fibrosis are seen in various tissues, and blood vessels may show intimal fibrosis, endothelial proliferation, and hyperplasia of the media. Although many facts are known about progressive systemic sclerosis, a unified, workable hypothesis that would account for its various clinical manifestations has not yet been put together.
14. Cole BC, Taylor MB, Ward JR: Studies on the infectious etiology of human rheumatoid arthritis: II. Search for humoral and cellbound antibodies against mycoplasmal antigens. Arthritis Rheum 18:435, 1975
16. Winfield JB, Winchester RJ, Wernet P et al: Antibodies to lymphocytes and the estimation of B and T cells in the connective tissue disorders. In Beers RF, Bassett EG (eds): The Role of Immunological Factors in Infectious, Allergic, and Autoimmune Processes, p 137. New York: Raven Press, 1976
22. Freland SS, Natvig JB, Wisloff F et al: Lymphocyte reactions in rheumatoid arthritis. In Beers RF Jr, Bassett EG (eds): The Role of Immunologic Factors in Infectious, Allergic, and Autoimmune Processes, p 289. New York: Raven Press, 1976
28. Schaller JG, Johnson GD, Holborow EJ et al: The association of antinuclear antibodies with the chronic iridocyclitis of juvenile rheumatoid arthritis (Still's disease). Arthritis Rheum 17:409, 1974
46. Hawkins D: Diffuse connective tissue diseases: I. Systemic lupus erythematosus and related disorders, pp 256–294. In Freedman SO, Gold P (eds): Clinical Immunology, 2nd ed. Hagerstown: Harper & Row, 1976
60. Fraga A, Mintz G, Valle L et al: Takayasu's arteritis: Frequency of systemic manifestations (study of 22 patients) and favorable response to maintenance steroid therapy with adrenocorticosteroids (12 patients). Arthritis Rheum 15:617, 1972