Reduced T-lymphocyte subsets in systemic lupus erythematosus: Effects of immune complexes and lymphocytotoxic antibodies

Abstract

Patients with active systemic lupus erythematosus (SLE) show significant reductions of T cells with receptors for the Fc portion of IgG, Tγ cells, which have been found to suppress in vitro B-cell responses to pokeweed mitogen. T cells with receptors for the Fc portion of IgM, Tμ cells, which show both helper and suppressor functions, are also reduced in SLE. Levels of both Tγ and Tμ cells in patients with inactive disease are intermediate between those of patients with active SLE and normal individuals. In a majority of individual patients, levels of Tγ cells were found to fluctuate with disease activity. SLE patients with reduced levels of Tγ cells showed high levels of circulating immune complexes, although a uniform inverse correlation was not detected. The pathophysiologic mechanisms in the observed decrease of T-cell subsets in SLE patients were studied by determination of the effect of aggregated IgG (an in vitro model of immune complexes) and lymphocytotoxic antibodies on T-cell subsets from normal individuals. Addition of aggregated IgG led to irreversible reduction of Tγ cells with no effect on Tμ cells. By contrast, both types of T-cell subsets were reversibly decreased by SLE sera with lymphocytotoxic antibody activity. Thus the observed decrease in T-cell subsets appears to be secondary to both immune complexes and lymphocytotoxic antibodies in SLE patients, and is reversible with remission of disease activity. Analysis of T-cell subpopulations in SLE appears to reflect other laboratory parameters associated with disease activity in these patients.