Reversible interleukin-2 response defects in systemic lupus erythematosus.

Limiting dilution analysis techniques were used to determine precursor frequencies for interleukin-2 (IL-2) responsive cells among the peripheral blood lymphocytes of patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis compared with healthy subjects. Response defects in SLE were found, but were of two types: reduced precursor frequencies with normal pattern of response (single-hit kinetics); and abnormal multi-hit responsiveness. These abnormalities were not more frequent statistically in those with active disease. Precursor frequencies of SLE peripheral blood lymphocytes were enhanced by resting the cells for up to 72 h prior to activation, and by adding exogenous IL-2 during the initial activation step. The IL-2 response defects of SLE are therefore reversible and may in part be secondary to other in vivo abnormalities, such as deficient IL-2 production.