In vitro suppressor T lymphocyte dysfunction in autoimmune thrombocytopenic purpura associated with a complement-fixing antibody.

Ig secretion of peripheral blood mononuclear cells (PBMC) was measured in Epstein Barr virus (EBV) seropositive autoimmune thrombocytopenic purpura (ATP) patients and controls following in vitro infection with EBV. EBV infected PBMC from patients with ATP secreted Ig for a longer period of time than EBV infected control cells and had higher peak Ig production. Removal of T cells or CD8 cells from control PBMC increased the duration and level of Ig production to that achieved by ATP PBMC. Total T or CD8 cell depletion of ATP PBMC had no effect on the enhanced level or duration of Ig secretion. Depletion of control CD4 lymphocytes decreased Ig production. Treatment of EBV infected control PBMC with either ATP sera or purified IgG (plus complement) increased the duration and level of production of Ig to that observed in ATP PBMC, control PBMC depleted of all T cells or control PBMC depleted of CD8 cells. This antibody effect could be reversed by reconstitution with control T cells. Thus, patients with ATP produce an antibody which leads to suppressor cell dysfunction. Defective function of these cells may lead to a disorder of immune regulation in which autoantibodies are produced against platelets.