Assessment of in vivo frequency of mutated T cells in patients with systemic lupus erythematosus

The frequency of mutant T cells (FMC) in blood lymphocytes from patients with systemic lupus erythematosus (SLE) was measured by growing cells in the presence and in the absence of 6-thioguanine. Patients with SLE had a spectrum of FMC ranging from normal to about 100 times normal. This high FMC among cells from SLE patients appears to reflect excessive in vivo activation and proliferation during the course of the disease. This represents the first demonstration of such a T cell abnormality in SLE; it supports the hypothesis that SLE T cells demonstrate increased in vivo division and/or survival.