21 patients with criteria for systemic lupus erythematosus (SLE) and 12 normal controls were studied for their spontaneous circulating IgM and IgG plaque-forming cells (PFCs) reactive against sheep erythrocytes (SRBC) and against a panel of five haptens. Quantitatively defined active and mildly active SLE patients had significantly elevated IgM- and IgG-producing PFCs in their peripheral blood reactive with the panel of five chemically defined haptens. Those patients having inactive SLE also showed increased circulating IgM PFCs. Significant elevations in circulating hapten-reactive PFCs were found to correlate progressively with disease activity in the inactive, mildly active, and active SLE patient groups. Circulating IgM- and IgG-secreting PFC reactive against SRBC were both significantly elevated only in those patients with active SLE. The data support the concept that SLE patients have a generalized increase in B cell activity against a broad repertoire of determinants, even those ostensibly unrelated to natural tissue antigens.

Genetic, environmental, and immune factors have been implicated in the pathogenesis of active systemic lupus erythematosus (SLE). To investigate the basis for abnormalities in immune regulation, we studies lymphocytes from patients with SLE during the active and inactive phases of their disease to examine their ability to develop Con A induced suppressor function (5 patients) and to develop a normal autologous mixed lymphocyte reaction (MLR) (7 patients). In each case results of these in vitro tests using whole T cells were abnormal during the active phase of the disease and returned to normal when the disease activity decreased. The results of this study suggest that the abnormalities of suppressor cell generation and the autologous MLR observed in whole T cell populations from patients with active SLE are not solely due to intrinsic and invariant lymphocyte defects. They further suggest that loss of immune regulatory function is not a simple genetically determined trait since the regulatory function returned to normal when the disease became inactive. However, these results do not exclude an underlying genetic effect on the immune system which requires a second factor (such as an environmental trigger) for expression. Evidence in support of this latter possibility derives from studies of Tγ cells. Fractionation of the functionally normal whole T cells from some patients who were clinically inactive revealed impaired function of Tγ cells. This subset of T cells may be easily perturbed by stimuli not sufficient to cause clinically apparent disease.

The mechanism through which interferon exerts immunoregulatory influence on antibody production in autoimmune NZB mice and normal Balb/C mice was studied. Interferon suppressed T cell-dependent anti-SRBC response in normal mice indirectly by activating suppressor T cells. The suppressor cell activity induced by interferon is mediated by Ly123⁺ cells presumably acting as feedback regulators for the suppression.

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