Activation-induced cell death (AICD) plays an important role in the regulation of the immune response by eliminating preactivated and potentially autoreactive cells. To elucidate possible abnormalities of AICD in human systemic lupus erythematosus (SLE), we studied AICD in activated T cells from patients with SLE and normal controls. CD3-mediated cell death was determined in short-term T cell lines by flow cytometry using propidium iodide staining and analysis of DNA subdiploid peak populations. It was found to be significantly lower in T cells from SLE patients compared to cells from normal controls. Anti-Fas mAb-mediated cell death was similar in SLE and control cell lines. CD3-mediated AICD could be blocked in control and SLE T cell lines by an IgG anti-Fas mAb. Indirect immunofluorescence analysis showed statistically significantly less intracellular TNF-alpha in SLE T cells than in control cells. These data show that activated T cells from patients with SLE are relatively resistant to a TCR-mediated death stimulus although they display intact anti-Fas mAb-mediated cell death. Defective antigen-mediated cell death can contribute to increased numbers of activated autoreactive cells in lupus patients.