Relationship of lymphocytotoxic antibodies to lymphopenia and parameters of disease activity in systemic lupus erythematosus.

Peripheral blood lymphocyte subpopulations determined in 40 patients with systemic lupus erythematosus, revealed significant lymphopenia in comparison to normal controls. The lymphopenia was caused by decreases in the absolute numbers of both T cells and surface immunoglobulin bearing (SIg) cells. There were significant percentage decreases in T cells and normal percentages of SIg cells, resulting in an increased percentage of "null" cells. The lymphopenia was significantly greater in patients considered to have active disease on the basis of clinical parameters, and was strongly correlated with lymphocytotoxic antibodies, DNA antibodies, and hypocomplementemia. The lymphocytotoxic antibodies were reactive with both T and B lymphocytes from normal and ill donors, human organs, and various lymphoblastoid cell lines. In 30 patients who were followed for up to 22 months, the lymphopenia was clearly seen to develop during, but not before, periods of clinical disease activity, independent of changes in therapy.