Abnormal responses of rheumatoid arthritis lymphocytes to Epstein-Barr virus infection in vitro: evidence for multiple defects

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

Lymphokine-activated killer cell activity in rheumatoid arthritis

The lymphokine-activated killer (LAK) cell activity in the peripheral blood of 23 patients with rheumatoid arthritis has been studied. Two control groups comprised (a) nine patients with another chronic inflammatory disease (sarcoidosis) and (b) 19 normal healthy volunteers. The LAK activity induced by human recombinant IL-2 was very similar in controls and patients with rheumatoid arthritis but was significantly decreased in patients with sarcoidosis, although the frequency of LAK-cell precursors measured using a limiting dilution assay was comparable in all three groups. The DNA synthetic response of peripheral blood mononuclear (PBM) cells to IL-2 was slightly decreased in patients with both rheumatoid arthritis and sarcoidosis as compared to controls, but this decrease was not statistically significant. Spontaneous DNA synthesis in PBM cells cultured in the absence of IL-2 was essentially identical in all three groups. We conclude on the basis of these results that the higher risk of non-Hodgkin's lymphomas in patients with rheumatoid arthritis cannot be attributed to an impairment of LAK activity. Furthermore, the doses of gamma-irradiation, which abolished the 'background' cytotoxicity of PBM cells cultured without IL-2 and also blocked effectively both spontaneous and exogenous IL-2-dependent DNA synthesis, had little effect on the generation of LAK activity. These observations are discussed in regard to the role of non-specific cytotoxic cells and the therapeutic efficacy of antiproliferative drugs in rheumatoid arthritis.

CD5 positive B cells in patients with rheumatoid arthritis: phorbol ester mediated enhancement of detection

CD5 molecules present on human T cells are detectable but weakly expressed on some human B cells. We have increased the sensitivity of their detection by treating the B enriched cells with phorbol myristic acetate (PMA), a tumour promoting agent. The numbers of CD5+ B cells in the blood of patients with rheumatoid arthritis (RA) were higher than in control blood, and after PMA treatment this was statistically significant. CD5+ B cells were also increased in tonsils, lymph nodes, and spleens after PMA activation. There were no significant differences between the percentages of B cells carrying chi or lambda light chains in their expression of CD5 molecules in patients with RA.

The abnormal cytotoxic T cell response to Epstein-Barr virus in rheumatoid arthritis is correlated with disease activity and occurs in other arthropathies

The cytotoxic T cell response to Epstein-Barr virus as measured by the regression assay was found to be impaired in a group of patients with active rheumatoid arthritis (RA). When these patients responded clinically to treatment with sulphasalazine there was a concomitant increase in the strength of this virus specific T cell response. The suggestion of a correlation between disease activity and impairment in this immune response was borne out in studies of other groups of patients with RA. Thus six out of 10 hospitalised patients had abnormal regression compared with six out of 31 patients seen routinely as outpatients. Studies of patients with inflammatory arthropathies other than RA, however, also showed abnormal regression in four out of 16 patients. It is concluded that the impairment in the cytotoxic T cell response to Epstein-Barr virus in RA is influenced by disease activity, and that this abnormality is not a specific feature of rheumatoid disease.

The effects of cyclosporin A on the early responses of B and T cells to Epstein-Barr virus infection

The immunosuppressive properties of the fungal metabolite Cyclosporin A (CsA) on the human lymphocyte response to the polyclonal B cell activator Epstein-Barr virus (EBV) in vitro were assessed. CsA showed both stimulatory and inhibitory effects on EBV-induced IgM secretion, the net effect being dependent on the dose of virus used. T cells were required for both these effects to occur. A model is proposed to account for the complex interactions of CsA in this system.

Defective Epstein-Barr virus specific suppressor T cell function in progressive systemic sclerosis

Several immunoregulatory defects of Epstein-Barr virus (EBV) induced B cell activation have been described in patients with rheumatoid arthritis (RA), suggesting that EBV may have a role in the pathogenesis of RA. We assessed EBV specific T cell regulation in 20 patients with progressive systemic sclerosis (PSS) and immune to EBV and in 10 control subjects also immune to EBV by comparing the secretion of IgM into supernatants of 16 day cultures of B cells alone and cocultures of B and autologous T cells. In control subjects autologous T cells mediated a significant decrease in the secretion of IgM by B cells at 12 and 16 days of culture. Analysis of individual responses showed the existence of two subgroups of patients with PSS: group I (10 patients) had a suppressor T cell function similar to that of controls; group II (10 patients) had a defective T cell function. Differences in the duration or severity of the disease, the slow acting therapeutic agents, and anti-inflammatory drugs could not account for these subdivisions. These results suggest that several immunoregulatory defects of EBV induced B cell activation exist in different connective tissue diseases.

Modulation of Epstein-Barr virus-induced B-cell activation by concanavalin A

Direct addition of the T-cell mitogen, concanavalin A (Con A), to cultures of Epstein-Barr virus (EBV)-stimulated peripheral blood mononuclear cells (PBMC) resulted in a dose-dependent inhibition of immunoglobulin M (IgM) secreted in the supernatant, as measured by an enzyme-linked immunosorbent assay. Furthermore, Con A inhibited IgM secretion of isolated T-depleted cells stimulated with EBV, and both the proliferation and IgM secretion of EBV-driven lymphoblastoid cell lines. T-Enriched cells, precultured for 48 hr with Con A, were also able to suppress the IgM response of fresh autologous PBMC stimulated with EBV. This suppression was radiation sensitive (2000 rad), a procedure which resulted in enhancement of the IgM secretion of the responder cells in two out of three experiments. Studies on the long-term effects of Con A showed that the early suppression of IgM secretion was transient and that the mitogen prevented the development of the cytotoxic T-cell response normally seen with lymphocytes from EBV-seropositive donors after 5 weeks of culture. Thus, Con A appears to modulate human lymphocyte responses to EBV by multiple mechanisms.

A cell surface monoclonal antibody (H366) helps to discriminate human cytotoxic from suppressor T cells

A study has been undertaken to differentiate T cytotoxic (Tc) and T suppressor (Ts) cell subsets using a monoclonal antibody termed H366 (mouse IgG2b) previously reported to phenotype natural killer and killer (NK/K) cells. Mononuclear cell suspensions from 14 normal subjects were depleted of H366+ cells by means of complement dependent cytotoxicity and the remaining cells were phenotyped with CD8 and CD4 monoclonal antibodies. The effects of depletion with H366 plus complement (C1) on the induction and activity of suppressor and cytotoxic T cells was also examined. The results indicate that H366 antibody recognizes in addition to NK/K cells, a population of Tc but not Ts or helper cells. Therefore, H366 antibody can be useful for obtaining Ts enriched lymphocyte subpopulations and this property may also be used for the enumeration of suppressor cells in the peripheral blood in disease states.