Cells In Rheumatoid Arthritis Patients Research Articles

Oligoclonality of V beta 3 TCR chains in the CD8+ T cell population of rheumatoid arthritis patients.

It has been established that oligoclonal expansion is a common feature of the CD8+ T cell population, particularly within the CD8+ CD57+ lymphocyte subset. In addition, clonal malignancies involving CD8+ CD57+ T cells (large granulocytic lymphocytic leukemias) are often accompanied by rheumatoid arthritis, Felty's syndrome, or both. Therefore, to identify disease-related alterations in the CD8+ T cell repertoire, we have compared the patterns of oligoclonality in the CD8+ T cells of rheumatoid arthritis patients (n = 32) with those of age-matched controls (n = 25). By using a multiplex PCR assay for the CDR3 length of TCR beta-chains, we have found a striking increase in the frequency of CD8+ oligoclonality involving V beta 3 TCR: 50% of the rheumatoid arthritis patients had evidence of oligoclonality in this TCR family compared with 4% of controls (p < 0.0002). In addition, two unrelated RA patients had clonally dominant CD8+ T cell beta receptors that were identical in amino acid sequence, suggesting selection by a common Ag. An analysis of a subset of RA patients with mAbs specific for V beta 3 TCR revealed the presence of clonal expansion in a minority of patients usually, but not exclusively, involving the CD57+ subset. These data define a phenotype of the T cell repertoire that is strongly associated with rheumatoid arthritis; the mechanisms and genetic and environmental factors that explain this phenomenon remain to be defined.

Role of tumor necrosis factor‐α in the regulation of activated synovial T cell growth: Downregulation of synovial T cells in rheumatoid arthritis patients

To characterize the role of tumor necrosis factor (TNF)-alpha in regulating synovial T cell growth, cell cycle progression associated with TNF-alpha in mitogen-activated synovial T cells of patients with rheumatoid arthritis (RA) were analyzed. After mitogen stimulation, the majority of synovial T cells in RA patients accumulated in S-phase. Anti-human TNF-alpha monoclonal antibody and soluble recombinant human TNF receptor (rhTNFR) can block S-phase accumulation. Furthermore, synovial fluid (SF) from RA patients was able to inhibit the proliferation of these S-phase-accumulated T cells. These data indicate that TNF-alpha could regulate activated synovial T cell growth by driving them into S-phase. Combined with the activities of other components of SF, TNF-alpha seems to play an important role in down-regulating activated synovial T cells in RA patients. In addition, the elevated level of soluble TNFR in the SFof disease-active RA patients is believed to be associated with the promotion of synovial T cell responses.

VH3-21 B Cells Escape from a State of Tolerance in Rheumatoid Arthritis and Secrete Rheumatoid Factor

Rheumatoid factor (RF) is a characteristic but not pathognomic feature in patients with rheumatoid arthritis (RA). It is unknown whether the repertoire of immunoglobulin genes utilized by RF+ B cells of RA patients is unique and whether RF+ B cells in normal individuals are silenced or deleted. Clonal B cell populations were established from the peripheral blood of normal donors (127 B cell clones), RA patients (113 RF- and 60 RF+ B cell clones) and patients with primary Sjögren's syndrome (82 RF- and 47 RF+ B cell clones) by coculturing with anti-CD3-stimulated T helper cell clones. The cross-reactivity pattern of antibodies secreted by the B cell clones was determined by ELISA on a panel of antigens. The molecular structure of the IgM heavy chains was characterized by VH family-specific RT-PCR and sequencing. VH elements which correlated with RF specificity were identified. The responsiveness of B cells expressing these VH elements to T helper cell signals was compared in normal individuals and RA patients. The majority of RF+ B cells were monospecific when specificity was tested on five antigens. RF+ B cells expressed a significantly different repertoire of VH gene segments than RF- B cells. In particular, the VH3 gene segment V3-21 was not detected in B cell clones from normals but was the most frequent VH element in RF+ B cell clones from RA patients. Most of the V3-21 sequences were in germline configuration. The correlation between RF specificity and V3-21 gene segment usage was maintained in patients with Sjögren's syndrome. V3-21 transcripts were present in peripheral blood B cells from normal individuals. VH3-21+ B cells from RA patients but not from normal donors were responsive to preactivated T helper cells. Stimulation with a bacterial superantigen could overcome the nonresponsiveness of V3-21+ B cells in normal donors and induce the secretion of RF. RF production is correlated with the usage of the V3-21 gene segment in two distinct RF+ diseases. In patients with these diseases, V3-21+ B cells secrete antibodies with RF activity in response to activated T helper cells. V3-21+ B cells remain in a state of nonresponsiveness in normal individuals that can be broken by superantigen stimulation. The germline configuration of VH3-21+ RF+ immunoglobulins in RA patients suggests that the loss of tolerance is not an antigen-driven process.

Cd28 expression on t cell subsets in vivo and cd28‐mediated t cell response in vitro in patients with rheumatoid arthritis

In view of the critical importance of the CD28-CD80 (B7/BB1) costimulatory pathway in antigen-specific T cell activation and clonal expansion, we examined CD28 surface molecule expression in vivo, and T cell receptor/CD3-mediated and B7/BB1-costimulated T cell proliferation in vitro, in rheumatoid arthritis (RA). Two-color immunofluorescence analyses of peripheral blood and synovial fluid-derived T cells, as well as 3H-thymidine incorporation assays, were performed. In the peripheral blood of 31 patients with active, untreated RA, a mean of 91% (range 48-100%) of CD4+ and 46% (range 13-82%) of CD8+ T cell subsets were CD28+, which was not significantly lower than normal. Although an overall decrease in the number of T cells was not observed, the numbers of CD28+CD8+ T cells were significantly lower in RA patients (mean 233/microliters, versus 292/microliters in controls), and this decrease was more pronounced in patients with severe disease (mean 172/microliters). CD28 expression on peripheral CD8+ T cells in RA patients, but not in healthy individuals, correlated inversely with T cell activation as assessed by HLA-DR antigen expression. In contrast to the peripheral blood, RA synovial fluid T cells were almost exclusively CD28+, suggesting that migration of CD28+CD8+ T cells to active sites of inflammation may occur. In vitro proliferative responses of peripheral blood T cells to B7/BB1 costimulation in the presence of mitogenic doses of anti-CD3 monoclonal antibody were identical in patients with RA and healthy individuals. Functionally intact CD28+ T cells may contribute to the abnormal immunoregulation and joint inflammation in RA.

5-aminoimidazole-4-carboxamide ribotide (AICAR) and its metabolites: metabolic and cytotoxic effects and accumulation during methotrexate treatment

Methotrexate is an antifolate useful in the treatment of neoplastic and non-neoplastic diseases. The mechanism of action of low dose methotrexate in the treatment of autoimmune diseases is unclear. It is known that methotrexate treatment blocks de novo purine biosynthesis, resulting in the accumulation of the intermediate 5-aminoimidazole-4-carboxamide ribotide and its metabolites. It is hypothesized that these substances are involved in the mechanism of action of low dose methotrexate therapy by inhibiting enzymes crucial to immune function. 5-aminoimidazole-4-carboxamide ribotide and its riboside were found to be irreversible inhibitors of S-adenosyl homocysteine hydrolase (EC 3.3.1.1) using enzyme from peripheral blood mononuclear cells of rheumatoid arthritis patients and from rabbit erythrocytes. 5-aminoimidazole-4-carboxamide was also found to be a competitive inhibitor (with respect to adenosine) of peripheral blood mononuclear cells adenosine deaminase (EC 3.5.4.4) and S-adenosyl homocysteine hydrolase. Methotrexote, at concentrations similar to blood levels of low-dose-treated patients (i.e., 10 and 20 nm), was cytotoxic to a culture of a human lymphoblast T cells but not to a culture of a human lymphoblast B cells. 5-aminoimidazole-4-carboxamide ribotide accumulated in T cells but not B cells treated with methotrexate, and 5-aminoimidazole-4-carboxamide-riboside potentiated methotrexate toxicity only in T cells. A reduction in the activity of phosphoribosyl-aminoimidazole carboxamide formyltransferase (EC 2.1.2.3) was observed in methotrexate-treated cultures of T cells but not B cells. The S-adenosyl homocysteine hydrolase activity of cultured T cells was more sensitive to inhibition by 5-aminoimidazole-4-carboxamide riboside in the medium when compared with B cells. No substantial reduction of adenosine deaminase or S-adenosyl homocysteine hydrolase activities was observed in methotrexate treated cultures of T or B cells. The data suggest that 5-aminoimidazole-4-carboxamide ribotide and 5-aminoimidazole-4-carboxamide-riboside have the potential for interfering with both adenosine deaminase and S-adenosyl homocysteine hydrolase, enzymes crucial to normal immune function. Methotrexate cytotoxicity was associated with 5-aminoimidazole-4-carboxamide ribotide accumulation and an inhibition of 5-aminoimidazole-4-carboxamide ribotide transformylase. The fact that 5-aminoimidazole-4-carboxamide-riboside potentiates methotrexate cytotoxicity in T cells may also be related to the fact that its S-adenosyl homocysteine hydrolase is relatively sensitive to inhibition by 5-aminoimidazole-4-carboxamide-riboside. Dilution of inhibitors during enzyme assays may account for the fact that little or no decrease in the S-adenosyl homocysteine hydrolase or adenosine deaminase activities were observed in the methotrexate-treated cells. The data are consistent with a methotrexate-induced cytotoxicity targeted toward T cells, a cell type implicated in the pathology of autoimmune disease.

Preferential utilization of a novel V lambda 3 gene in monoclonal rheumatoid factors derived from the synovial cells of rheumatoid arthritis patients.

To further our understanding about the molecular genetics of rheumatoid factor (RF) in rheumatoid arthritis (RA). The heavy and light chain variable region (V) genes of 5 new human monoclonal IgM RFs were cloned and sequenced using the polymerase chain reaction and the dideoxynucleotide termination method. The results reveal the recurrent usage in two RA patients of a novel V lambda 3 germline gene, designated Humlv3c93. Specifically, in 2 of 3 RFs (C93 and D53) from one patient, the light chains in the V lambda gene-encoded region were identical to each other and to the light chain of an RF (H4) from another patient. Serologically, the light chains of these 3 RFs were classified as members of the V lambda 3b sub-subgroup. Each of the RFs was encoded by a different VH gene. Both C93 and D53 bound specifically with human and rabbit IgG, whereas H4 was monospecific for rabbit IgG. Since the lv3c93 gene is not homologous to any reported V lambda sequence from natural autoantibodies, it is possible that lv3c93 may represent a disease-specific RF-related V lambda gene. Moreover, the amino acid sequence CSGGSCY in the third complementarity-determining regions of 2 of the RF heavy chains is encoded by the DLR2 gene segment and has been found previously in 2 other RA-derived RFs, and thus may play a significant role in antigen binding.

Characterization of monoclonal antibodies specific for the Vβ3 family of the human T cell receptor generated using soluble TCR β-chain

A soluble, recombinant form of the human T cell receptor (TCR) β-chain containing the Vβ3.1 sequence has been constructed, expressed in Chinese hamster ovary cells, amplified by dihydrofolate reductase selection, and purified in quantities appropriate for the generation of monoclonal antibodies (mAb). The Vβ3 sequence was chosen because of its reported elevated usage in the synovial T cells of rheumatoid arthritis patients but the approach described should be applicable to other known human Vβ gene sequences. By this method, two mAb were prepared which reacted with up to 10% of normal, live peripheral blood T cells but with reactivity varying greatly among individual donors. Both mAb specifically bound to a murine T cell line transfected with a human TCR Vβ3.1 and immunoprecipated a protein of the expected molecular weight for the TCR β-chain. Both antibodies were mitogenic for T cells and analysis of peripheral blood lymphocyte cultures stimulated with the mAb suggested that both were specific for the Vβ3.1 subfamily and not Dβ or Jβ. Clones expressing Vβ3, which were derived from mAb-stimulated peripheral blood lymphocytes of a single individual, preferentially (8/13), but not exclusively, utilized the Jβ2.7 gene segment. The Vβ3.1 usage showed no preference for the CD8 + or CD4 + subpopulations of normal peripheral blood T cells.

Beta 1 integrin-mediated interaction with extracellular matrix proteins regulates cytokine gene expression in synovial fluid cells of rheumatoid arthritis patients.

Inflammatory cytokines have been implicated in the pathogenesis of rheumatoid arthritis (RA), whereas the mechanisms for constitutive production of inflammatory cytokines in affected joints are largely unknown. Recently, integrin-mediated interaction with extracellular matrix (ECM) proteins has been demonstrated to play a role in regulating cytokine production in T cells and monocytes. In this study, we investigated the contribution of the beta 1 integrin-mediated interaction with ECM proteins to the persistent cytokine gene expression in RA synovial fluid mononuclear cells (SFMNC). We examined mRNA expression of 14 cytokines in the SFMNC of three RA patients, which were either fresh or cultured overnight in serum-free medium on ECM-coated plates, by polymerase chain reaction with a panel of oligonucleotide primers specific for each cytokine. The persistent expression of various cytokine mRNA found in fresh SFMNC was maintained after overnight culture in serum-free medium on ECM proteins, especially on laminin (LM), but not on serum albumin. This effect of LM was inhibited by an anti-integrin beta 1 chain (CD29) mAb, as well as by an anti-CD3 mAb, indicating an important role of the beta 1 integrin-mediated interaction with ECM proteins in regulating persistent cytokine gene expression in RA SFMNC, and a key role of T cells in regulating inflammatory monokine production.

Lack of preferential V beta usage in synovial T cells of rheumatoid arthritis patients.

The T-cell receptor V beta subfamily repertoires of synovial and peripheral T cells of 8 rheumatoid arthritis (RA) patients were determined using the polymerase chain reaction. Three normal controls were included. Some of the rheumatoid synovial samples did not express the complete range of V beta families and lacked as many as 6 gene families. However, these patients showed considerable individual variation in expression. Overall, the data do not support preferential T-cell receptor V beta usage in synovial T cells of RA patients either in comparison to their autochthonous peripheral T cells or to peripheral T cells of normal subjects.

Possible role of CD5+ B cells expressing CD23 in mediating the elevation of serum-soluble CD23 in patients with rheumatoid arthritis.

Since increased levels of serum soluble CD23/Fc epsilon RII (sCD23) were evidently demonstrated in patients with autoimmune diseases such as rheumatoid arthritis (RA), the possible mechanisms responsible for the elevation of serum sCD23 were investigated in RA patients. In keeping with increased serum sCD23, high proportion of CD23+ B cells was detected in the patients; this was associated with the enhanced expression of only Fc epsilon RIIa mRNA. Upon incubation at 37 degrees C, peripheral blood mononuclear cells of the patients spontaneously released high levels of sCD23 into the culture supernatant, while the CD23 expression on their B cells was considerably maintained even after the culture. Dot blot analysis further revealed that in contrast to normal subjects, RA patients showed no complete disappearance of Fc epsilon RIIa mRNA after the spontaneous culture. In addition, sCD23 release was significantly reduced in the patients by the addition of cycloheximide. It was also found that cycloheximide exerted the inhibitory influence on the spontaneous culture-mediated expression of CD23 on CD5+ but not CD5- B cells of the patients. However, the disappearance of CD23 from CD5+ as well as CD5- B cells of cord blood samples was unaffected by the agent. These results strongly suggest that CD5+ B cells of RA patients may be specifically activated by some mechanisms responsible for the persistent expression of Fc epsilon RIIa mRNA leading to the accelerated turnover of CD23 and in turn the increased release of sCD23.

Gold-specific T cells in rheumatoid arthritis patients treated with gold.

Gold-specific T lymphocyte clones were isolated from a patient with rheumatoid arthritis who developed delayed type hypersensitivity reactions to gold. All of the isolated T cell clones required histocompatible antigen presenting cells as well as gold for induction of proliferation. Using a panel of HLA-homozygous Epstein Barr virus-transformed B (EBV-B) cells and anti-HLA antibodies, the clones were shown to recognize gold in the context of DR1 molecules. Gold recognition did not require active antigen processing since specific proliferation was not affected by glutaraldehyde fixation of the DR1 homozygous antigen presenting cells. Furthermore, we could show that gold salts inhibited peptide-induced responses of a peptide-specific T cell clone. In addition to providing evidence for gold-specific T cells in gold-treated RA patients exhibiting delayed type hypersensitivity responses, these data suggest that gold can alter MHC-peptide complexes. The latter observation may in part explain the mechanism/s responsible for both the therapeutic and the toxic effects of gold.

Activation of Murine Autoreactive B Cells by Interleukin 1-Like Factors Released from Synovial Inflammatory Cells of Rheumatoid Arthritis Patients

The effect of interleukin 1 (IL-1)-like factor(s), produced by cells isolated from the synovial fluids of rheumatoid arthritis (RA) patients, on an in vitro murine model of spontaneous autoimmunity, i.e., the development of plaque-forming cells (PFC) to bromelain-treated mouse red blood cells (Br-MRBC) in mouse peritoneal cell (PC) cultures, has been investigated. It has been found that IL-1-containing culture supernatants from cells isolated from joint fluids of RA patients, as well as recombinant IL-1, determine a marked increase in anti-Br-MRBC PFC development. Moreover, factor(s) of 10-20 KD molecular weight, with IL-1-like biological activity, capable of increasing the anti-Br-MRBC PFC development in mouse PC cultures, have been demonstrated in joint fluids from RA patients. The finding that synovial inflammatory cells produce factors that activate autoreactive B cells further supports the role of autoimmunity in the pathogenesis of rheumatoid arthritis, as self-perpetuing disorder.

High antigen reactivity in mononuclear cells from sites of chronic inflammation

Antigen-specific in-vitro responses of mononuclear cells from synovial fluid and peripheral blood of patients with rheumatoid arthritis were compared with those of mononuclear cells from pleural exudate and peripheral blood of non-rheumatoid-arthritis patients with chronic pleuritis not caused by tuberculosis. The antigens tested were an acetone-precipitable fraction of Mycobacterium tuberculosis (AP-Mt), an Escherichia coli lysate containing the 65 kD heat-shock protein of MbovisBCG (65 kD/Ecoli), the Mbovis heat-shock protein alone (65 kD), and E coli alone. The mean proliferative responses to AP-Mt were higher in synovial-fluid than in peripheral-blood mononuclear cells in rheumatoid arthritis patients (mean [SEM] stimulation index 10·5 [3·1] vs 2·6 [0·9]) and in pleural-exudate than in peripheral-blood mononuclear cells in the pleuritic patients (7·5 [1·7] vs 3·5 [2·0]). The same pattern was seen for the other three antigens. Only 1 of 26 synovial-fluid mononuclear cell samples from rheumatoid arthritis patients showed a positive response (stimulation index 3 or more) to 65 kD compared with 5 of 22 pleural-exudate mononuclear cell samples, so 65 kD seems not to be the major antigen recognised by synovial-fluid T cells in rheumatoid arthritis. Enhanced reactivity against mycobacterial and other bacterial antigens is not restricted to mononuclear cells from chronically inflamed joints but seems to be a common feature of chronic inflammation.

Expression of Activation Antigens on T Cells in Rheumatoid Arthritis Patients

The aim of our study was to identify differences in cell surface marker expression between T cells taken from the peripheral blood (PB) of healthy individuals and T cells recovered from inflamed joints of rheumatoid arthritis (RA) patients. Out of 118 monoclonal antibodies (MoAbs) directed against activation antigens on haematopoietic cells, 12 MoAbs recognizing nine distinct surface molecules were selected after a screening procedure to study the expression of the corresponding antigens on T cells from the PB, synovial fluid and synovial tissue of RA patients, and also on T cells from PB and spleens of controls. Using two-colour flow cytometry and immunohistology we found the molecules B-C5, CD39, CD40, CD45 R0, CD54, CD76 and potentially 1D11 to be substantially up-regulated on T cells from various body compartments in RA patients. We thus could determine that the cell surface of T cells in RA patients not only differs in MHC class II expression, but also in a number of other activation-associated cell surface molecules from T cells in healthy individuals.

Differential immunological response of patients with rheumatoid arthritis towards two different Epstein-Barr virus strains: inhibition of interleukin-1 release by the B95-8, but not the P3HR-1 virus strain

An abnormal immune response towards the Epstein-Barr virus (EBV) has been documented in patients with rheumatoid arthritis (RA). To investigate whether these findings are due to the transformation event caused by EBV, RA blood mononuclear cells and monocyte-enriched preparations were incubated with two different EBV strains: the transforming virus secreted by the cell line B95-8 and the virus released by the P3HR-1 cell line that is not able to transform due to a small deletion in the U2 region of the virus genome. Immunological response was determined by the production of interleukin-1 (IL-1) and tumor necrosis factor (TNF) using ELISA and bioassay systems. There was a striking difference in cytokine measurements with a strong inhibition of IL-1 and TNF production after incubation with the B95-8 virus, but not the P3HR-1 virus. These data indicate that the disturbed reaction of the immune system towards EBV is either dependent on the full transformation of B cells in RA patients or alternatively due to the secretion of a cytokine inhibitor by the B95-8 cell line.

Monoreactive high affinity and polyreactive low affinity rheumatoid factors are produced by CD5+ B cells from patients with rheumatoid arthritis.

In patients with rheumatoid arthritis (RA), circulating CD5+ B lymphocytes, but not CD5- B lymphocytes, are increased in number and size, exist in an activated state, spontaneously proliferate, and secrete Ig that binds to the Fc fragment of IgG. By constructing continuous mAb-secreting cell lines from CD5+ B lymphocytes, the properties and dissociation constants (Kd) of these antibodies were determined. Two types of rheumatoid factors (RFs) with discrete reactivities were produced. The first type is polyreactive and binds with relatively low affinity (Kd, 10(-5) mol/liter) to the Fc fragment of IgG. These antibodies are similar to those produced by CD5+ B cells from healthy subjects. The second type of RF is monoreactive and binds with higher affinity (Kd, 10(-7) mol/liter) to the Fc fragment of IgG. These latter autoantibodies are produced by CD5+ B cells of RA patients, but not healthy subjects. Long-term longitudinal studies are needed to determine the role of these two types of RFs in the pathogenesis of RA.

The Leu-1 B-cell subpopulation in patients with rheumatoid arthritis.

Ly-1-B cells have been shown to be elevated in autoimmune mice, especially NZB, and to secrete IgM autoantibody, suggesting that Ly-1 B cells may participate in autoimmune diseases. In this study, B-cell populations carrying Leu-1, a human T-cell surface molecule homologous to mouse Ly-1 (Leu-1 B), were examined by dual fluorescence flow cytometry, in peripheral blood lymphocytes taken from patients suffering from various autoimmune disease. These B cells were shown to be present at a significantly high percentage in rheumatoid arthritis (RA) patients. There was no significant correlation among the incidence of Leu-1 B cells, rheumatoid factor (RF) titers, and the amount of IgM production in vitro. There was, however, a significantly high incidence of Leu-1 B cells in RA patients with a high RF titer (greater than 5 X 2(13), suggesting that these B cells in RA may play an important role in IgM RF production in vivo.

Characterization of T cells bearing HLA-DR antigens in rheumatoid arthritis.

It has been demonstrated that T cells bearing HLA-DR antigens on their surface are actively involved in an immune response. In diseases of disordered immunoregulation, including rheumatoid arthritis (RA), there are elevated numbers of circulating HLA-DR+ T cells. In this study, we examined the cellular physiology of these T cells in RA patients. Using tritiated thymidine incorporation, we found that, in most patients, HLA-DR+ cells do not account for a significant amount of spontaneous proliferation found in peripheral blood T cells. RNA hybridization studies, using a cloned HLA-DR alpha chain gene probe, indicate that the T cells actively synthesize HLA-DR antigens rather than passively adsorbing them. The cell surface phenotype of the HLA-DR+ T cells was analyzed using double immunofluorescence and a variety of monoclonal antibodies. The expression of T cell differentiation antigens T4, T6, T8, and T10 varied markedly from patient to patient. In some patients, a significant number of cells expressed both T4 and T8 antigens. Most HLA-DR+ cells also express antigens defined by the following antibodies: anti-Tac (the interleukin-2 receptor), J2 (a glycoprotein found on T cell blasts), and ILR-1 (a class II major histocompatibility complex antigen). Activated T cells bearing HLA-DR antigens may play a role in the development of RA. Our data demonstrate that although these cells are not lymphoblasts, they possess a distinct cell surface phenotype.

Characterization of blood mononuclear cells of rheumatoid arthritis patients: II. Depressed PPD presentation by monocytes to T lymphocytes

Purified blood monocytes from patients with rheumatoid arthritis (RA) were significantly less capable of presenting purified protein derivative of tuberculin (PPD) to autologous lymphocytes than monocytes from patients with osteoarthritis, degenerative spine diseases, or healthy controls. Since lymphocytes from RA patients exhibited a normal response to soluble PPD or concanavalin A, the lowered T-cell reactivity had to be attributed to a diminished antigen-presenting capacity of monocytes. Several reasons may be responsible for this altered monocyte function in rheumatoid arthritis: a shift of monocytes to subpopulations expressing less Ia-like antigens, an inherent monocyte disorder, or a “preactivation” of monocytes associated with a reduced antigen-presenting capacity.

Spontaneous DNA synthesis in rheumatoid arthritis: evidence of enhanced circulating non-T-cell proliferation.

3H-thymidine incorporation in cultures of peripheral blood mononuclear cells from patients with seropositive rheumatoid arthritis (RA) and healthy controls was measured in vitro in the absence of added stimulants. A significantly higher level of spontaneous DNA synthesis was found in cultures of mononuclear cells from patients with clinically active RA than from patients with inactive disease and normal controls. This activity was more apparent in 24-h cultures than in 72-h cultures. There was no correlation between DNA levels and IgM rheumatoid factor (RF) titres. When T- and non-T-cell populations were separated and cultured simultaneously with unfractionated cells, only non-T cells maintained high levels of DNA synthesis, and enrichment of surface membrane Ig+ (SmIg) cells was generally associated with enhancement of 3H-thymidine incorporation. Furthermore, no difference was found in spontaneous DNA synthesis between cultures either containing or depleted of phagocytic cells. Moreover, the addition of graded numbers of autologous monocytes to highly purified T- and non-T-cell populations did not alter the background DNA synthesis. Thus, endogenously activated cells in RA patients are neither T lymphocytes nor monocytes. A regulatory influence by monocytes could not be demonstrated. It is suggested that cells actively engaged in DNA synthesis in RA blood are non-T cells in origin, most probably B lymphocytes.