The cytotoxicity of leukocytes and lymphocytes from patients with rheumatoid arthritis for synovial cells

Synovial fibroblasts as target cells for staphylococcal enterotoxin-induced T-cell cytotoxicity

Rheumatoid arthritis (RA) is a chronic autoimmune disease of unknown aetiology. Recently, superantigens have been implied in the pathogenesis of RA. Superantigens activate a large fraction of T cells leading to the production of cytokines and proliferation. In addition, superantigens direct cellular cytotoxicity towards major histocompatibility complex (MHC) class II-expressing cells. There is now increasing evidence that cytotoxic T cells may be involved in the pathogenesis of RA. In the inflamed synovia class II-positive synovial fibroblasts (SFC) are found. In the present study it was tested whether MHC class II-positive SFC serve as target cells for superantigen-induced cellular cytotoxicity. SFC were stimulated with interferon-gamma to express class II antigens, then they were cultivated in the presence of CD4-positive T cells with or without staphylococcal enterotoxins (SE). Cytotoxicity of T cells was measured as release of lactate dehydrogenase from SFC. Specific cytotoxicity was only found in the presence of class II-positive SFC depending on the dose of SE. Maximum lysis was seen after 20 hr. T-cell cytotoxicity was inhibited by antibodies to MHC class II antigens. The data suggest that class II-positive SFC not only function as accessory cells for SE-mediated T-cell proliferation and interleukin-2 production but may also be the targets of superantigen-mediated cellular cytotoxicity.

Prospects of immunotherapy for rheumatoid arthritis

The main challenge in the development of new modalities for the treatment of rheumatoid arthritis is to enhance the specificity while reducing the adverse side-effects of therapeutics. Biotechnology provides a variety of reagents, such as monoclonal antibodies, recombinant cytokines, cytokine antagonists, and small peptides, with the potential to interfere with selected stages of the disease process in a highly specific manner. In addition, several new therapeutic approaches have emerged as a result of extensive research with animal models of disease, including T-cell vaccination and bone marrow transplantation. This article discusses current insights into the pathogenesis of rheumatic diseases, focusing on rheumatoid arthritis. A number of new therapeutic modalities for rheumatoid arthritis, in particular those acting on the immune system, are discussed. Because it is not possible to provide a complete overview of all the developments in the field in limited space, a selection of strategies and modalities which are representative of the broad variety of immunotherapeutic approaches currently used are highlighted.

Synoviocytes type A bind exogenous antigens recognized by antibodies present in rheumatoid arthritis

The presence of antibodies in rheumatoid arthritis (RA) patients to antigens on the synoviocyte surface has recently been reported (Scand. J. Immunol. 27, 295, 1988). Here we have further characterized these antigens and found that they are exogenous proteins acquired from the bovine serum used in the culture medium. By immunoprecipitation and ELISA studies, we have identified bovine albumin and transferrin as the antigens recognized by the RA antibodies. These specificities were found not only in the sera but also in the synovial fluid from RA patients. A comparative study with a large panel of RA sera did not show a correlation in the antibody specificities for bovine albumin, bovine transferrin, or the 65-kDa heat shock protein from Mycobacterium bovis. Similar experiments using rabbit and monkey sera as well as human synovial fluid and serum as a source of antigen did not reveal any reactivity with a highly positive RA serum. By sequence alignment, a high degree of homology between residues 142-156 from bovine albumin and residues 65-78 from human pro-collagen alpha 1 (I) was found. The capacity of the synoviocytes to bind exogenous antigens and the presence of antibodies to bovine proteins, normally present in the diet, suggest a role for these type A synoviocytes as well as a possible involvement of food antigens in the pathogenesis of RA.

Adjuvant-induced polyarthritis. Synovial cell activation prior to polyarthritis onset

We studied synoviocytes obtained from rats that had been injected with Freund's complete adjuvant 12 days prior to killing. We found that several activation parameters were affected in these synoviocytes, namely, the concanavalin A protein-binding pattern, the production of superoxide, and the appearance of the p77 polypeptide, which we have previously shown to be associated with the activation caused by the induction of polyarthritis. Our findings suggest that prior to the establishment of the inflammatory process, synoviocytes are in a state of activation, and may be a component of the molecular mechanism during the early stages of disease.

Autoantibodies from rheumatoid arthritis patients recognize antigens on the synoviocyte surface

We have found autoantibodies in the sera from rheumatoid arthritis (RA) patients which recognize two cell surface antigens of approximately 70 kDa and 28 kDa from synoviocyte extracts as detected by immunoprecipitation analysis. These polypeptides were immunoprecipitated from extracts containing mainly macrophage-like synoviocytes (type A) but not from extracts of homogeneous fibroblast-like synoviocytes (type B). These autoantigens are not selectively expressed by RA synoviocytes, since both RA and non-rheumatoid synovia were reactive for RA sera. From the panel of different RA sera tested, 64% immunoprecipitated the 70 kDa band, and 27% recognized the 28 kDa polypeptide. These differences in the specificity of the sera seemed to be related to the clinical state of the donor. The sera from patients suffering from other autoimmune diseases such as autoimmune thyroiditis and systemic lupus erythematosus (SLE) do not appear to be reactive for these specificities, but sera from patients with Sjögren's syndrome, psoriatic arthritis, and Crohn's disease showed a weak cross-reactivity with the 70 kDa polypeptide. This autoreactivity against synovial cells in RA supports the idea that these cells participate in the initial immune response of the disease.

Immunological aspects of the anemia of rheumatoid arthritis

In order to investigate the cause of the anemia concomitant with rheumatoid arthritis (RA), we examined, using the erythroid colony assay of human bone marrow colony-forming units-erythroid (CFU-e) and burst-forming units-erythroid (BFU-e), the effects of the patients' serum and peripheral blood T lymphocytes on the CFU-e-derived colonies. The counts of erythroid colonies of RA patients were markedly lower than those of human control subjects [CFU-e: control 152.9 +/- 30.6 (n = 19), RA 51.1 +/- 13.6 (n = 7), t = 7.66567, p less than 0.01; BFU-e: control 25.2 +/- 5.9 (n = 5), RA 12.6 +/- 2.6 (n = 7), t = 4.574, p less than 0.01]. The serum from two out of seven RA patients slightly inhibited the formation of CFU-e-derived colonies of human control subjects (t = 2.31, 0.05 less than p less than 0.1); however, the serum from the other five RA patients did not significantly inhibit human control erythroid colony formation as compared with human control serum (t = 0.981, 0.3 less than p less than 0.4). On the other hand, peripheral blood T lymphocytes of the patients markedly inhibited the formation of CFU-e-derived colonies of the control subjects as compared with peripheral blood T lymphocytes from human control subjects (t = 4.24, p less than 0.01). The above-mentioned results suggest that the peripheral blood T lymphocytes of RA patients might play a role as one of the causes of the concomitant anemia of RA patients.

Etiology of rheumatoid arthritis

Definite genetic associations with immunological cooperative HLA-D(R) antigens have been demonstrated for rheumatoid arthritis (RA). Microbial etiology has not been proven, but some hope for the supporters of this view is still given by small viruses, plasmids of enteric bacteria or perhaps oncogen-like DNA-sequences. Yet, electrophoretical analysis of membrane proteins or surface glycoproteins of RA synovial cells does not show any differences compared to reference cells. Autoimmunity to several tissue elements has been demonstrated, but most of it is of secondary nature. Antigenicities of type II and III collagens are probably only contributory factors for HLA-DR4 positive individuals. Proteoglycans or minor cartilage collagens have not been extensively studied, so far. Endocrine, dietary or psychological influences might be triggering events for otherwise 'preloaded' individuals.

Cellular immune function in rheumatic disease

Investigation of the cellular immune function in patients with rheumatic diseases is important in elucidating the pathogenesis of the disease processes and in determining the associated abnormalities of recognition and regulation exerted by the immune system. However, because of the lack of specificity and the variations noted from laboratory to laboratory, tests of cellular immune function are, at present, of little value in the laboratory diagnosis of these diseases. The abnormalities found in the rheumatic diseases occur with many autoimmune diseases and other inflammatory states. The common pathway of immune abnormalities appears to be influenced by several factors. They include several genetic loci, possible environmental factors, and immunologic mechanisms, which appear to interact in an intimate way to induce various autoimmune diseases.

Cellular immunity to possible synovial antigens in rheumatoid arthritis

A reaction has been demonstrated between extracts of synovial cells removed from intact rheumatoid knee joints and autologous leucocytes. The cell mediated immunity test system used was leucocyte migration inhibition. Variable reactions were found with a spectrum of allogeneic extracts when donor leucocytes came from married or transfused females or transfused males. Leucocytes from healthy (nontransfused) males showed no reaction with any of the extracts. As a period of cell culture was used prior to preparation of this extract to remove nonspecific inhibitory substances, native immunoglobulins, and complexes, the data are best explained by the presence of a foreign pathogen or altered cell component in the synovial cells of these rheumatoid patients.

Cell-mediated cytotoxicity for cultured autologous rheumatoid synovial membrane cells

Cytotoxicity tests were performed on cultured rheumatoid synovial membrane cells with autologous lymphocytes as effector cells. Three of 26 cultures were positive when tested at primary or first passage level, but on subsequent tests became negative. Tests based on an isotope-labelling technique and a micro-cytotoxicity assay were compared; the results appeared to correlate well. The expression of neoantigens on synovial cells was not demonstrated. Cultures initiated in medium containing hydrocortisone did not give rise to a population of synovial cells susceptible to immune lysis by autologous lymphocytes.

Familial rheumatoid arthritis: linkage of HLA to disease susceptibility locus in four families where proband presented with juvenile rheumatoid arthritis

The occurrence of a chronic seronegative polyarthritis has been studied in four families in which the proband presented with some form of juvenile rheumatoid arthritis. In these families, histocompatibility testing suggested that susceptibility to arthritis was controlled by a dominant allele with variable penetrance and expressivity at the rheumatoid-like arthritis, first locus (RLA-1). The combined lod scores for the four families (2.70) indicated that the odds in favor of genetic linkage between the major histocompatibility complex and the postulated disease susceptibility gene, RLA-1, were 500:1. In one family, a recombinant event permitted localization of RLA-1 centromeric to HLA-D. Of major interest was the fact that there was significant pleomorphism in the clinical manifestations of arthritis in affected individuals. In some, symptoms first occurred in childhood and in others, in adult life. Even among those with childhood-onset arthritis, different types of juvenile rheumatoid arthritis were observed within the same family.

Double-blind placebo controlled crossover evaluation of levamisole in rheumatoid arthritis

During levamisole therapy, 14 of 20 patients with previously unresponsive rheumatoid arthritis had significant improvement (P less than 0.05) in clinical measures of disease activity, erythrocyte sedimentation rate, and rheumatoid factor titer in a 32-week double-blind placebo controlled crossover trial. Levamisole was shown to alter antibody responses to tetanus and typhoid antigens, lymphocyte blastogenesis to phytohemagglutinins, and the number of null cells in peripheral blood. Agranulocytosis and rash resulted in discontinuation of the drug in one patient in each group. Though clearly effective, routine use of levamisole as a disease suppressant in rheumatoid arthritis must await more complete clarification of its association with agranulocytosis.

Studies of serum immunoglobulin binding to synovial fibroblast cell cultures from patients with rheumatoid arthritis

Using a sensitive 125I-protein A (PrA) binding assay to detect cell surface IgG, we have studied seven different synovial fibroblast cell cultures from patients with rheumatoid arthritis (RA). When these cultures were incubated in the presence of serum from 18 autologous and allogeneic RA patients (all seropositive), we were unable to detect significant IgG binding. Since IgM rheumatoid factor (RF) can block PrA binding, sera were absorbed with aggregated IgG to remove RF without affecting the results. Similar studies on three cell lines with seven rheumatoid sera were performed by antibody-dependent cell-mediated cytotoxicity. No significant cytotoxicity was observed. Since antibodies to collagen are present in rheumatoid sera, several cultures were incubated with ascorbic acid (12.5 microgram/ml) to optimize synthesis of cell surface collagen. These culture conditions did not affect serum immunoglobulin binding by the 125I-PrA assay. Thus, we can find no evidence for a direct humoral immune mediation of synovial proliferation in rheumatoid arthritis. These data do not support the hypothesis that the inflammatory process within the synovium of RA patients is an immunologic response to a fibroblast-associated antigen in the synovial membrane.

Measurement of immunoglobulin binding to synovial fibroblast monolayers: comparison of staphylococcal protein A binding to cytotoxic assay methods

We have studied the binding of rabbit antibody to cultured synovial fibroblasts by 3 methods: complement mediated cell lysis, 125I-labeled staphylococcal protein A ([125I]PrA) and antibody dependent cell mediated cytotoxicity (ADCC). The relative sensitivities of these 3 methods is 1 : 33 : 3300 respectively. The [125I]PrA binding method is shown to quantitatively detect cell bound IgG with a molar stoichiometry of approximately 1 : 1, protein A (PrA) to IgG if PrA is present in excess.

Immunopathologic studies of rheumatoid arthritis. I. Absence of complement-dependent cytotoxicity of rheumatoid sera for rheumatoid synovial cell cultures

A sensitive complement-dependent chromium release cytotoxicity assay was used to determine whether sera from rheumatoid arthritis (RA) patients contain antibody specific for an antigen on rheumatoid synovial cell cultures. Two hundred eight RA sera-RA synovial culture combinations were studied employing 21 sera and 16 synovial membranes; control combinations were derived from 5 normal sera and 10 degenerative joint disease synovial membranes. Anticomplementary activity of some rheumatoid sera was overcome using an increased complement concentration. The percent cytotoxicity of RA serum-RA culture combinations, both homologous and autologous, was not significantly greater than that of RA serum-control culture combinations. No correlation between duration of disease or duration of cell culture and percent cytotoxicity was found. Thus a unique antigen on cultured rheumatoid synovial cells was not recognized by rheumatoid serum antibody by use of this cytotoxicity assay.

Susceptibility of rheumatoid and nonrheumatoid synovial cells to antibody-dependent cell-mediated cytotoxicity

Fibroblastic cells derived from rheumatoid (RA) and nonrheumatoid (N-RA) synovial tissue (synovial cells) were used as targets in assays of antibody-dependent cell-mediated cytotoxicity (ADCC). Synovial cells that had been pretreated with human alloantisera were rapidly lysed by normal human blood mononuclear cells. RA and N-RA synovial cells were equally susceptible to ADCC under these assay conditions. Antibody to autologous synovial cells was not detected in sera from 10 patients with RA by this method of assay.

Cell-mediated immunity in rheumatoid arthritis

Cell-mediated immunity in rheumatoid arthritis (RA) was assessed by skin testing with six antigens in 107 patients, 94 of whom were age, sex, and race-matched with healthy individuals or patients with diseases unrelated to immunological abnormalities. 20% of RA patients were anergic. Impaired cell-mediated immunity in the RA patients was manifested by a decrease in the magnitude of skin reactivity as well as a decrease in the incidence of positive reactions to multiple antigens. Depression in cell-mediated immunity was related to age but not to sex, duration of disease, or disease activity. A slight correlation was found between absolute peripheral lymphocyte counts and the number of positive skin tests, and was confirmed by finding an association between lymphocyte counts and the size of skin reactions. A correlation was also found between lymphocyte counts and disease activity. Four explanations of the observed depression in cell-mediated immunity in RA were considered: (1) a preoccupation of the immune mechanism of the host with cell-mediated immunity reactions related to the pathogenesis of the disease; (2) a depression of cell-mediated immune reactivity by a virus infection; (3) depression of cell-mediated immunity by therapy; and (4) immune complex suppression of cell-mediated immunity. No effect of gold therapy was found. The near universal use of salicylates or other anti-inflammatory drugs did not permit investigation of the effect of these drugs on cell-mediated immunity.