Cytotoxic responses to alloantigens in systemic lupus erythematosus.

We have studied the ability of the peripheral mononuclear cells (MNC) from patients with systemic lupus erythematosus (SLE) to generate a cytotoxic (CML) response against alloantigens. CML responses in SLE patients were significantly lower than those of normal individuals. Mixed lymphocyte reaction (MLR) assays conducted in parallel in these patients were decreased but to a lesser extent. Some of the patients exhibited parallel decreases in both CML and MLR tests, while others showed decreased CML responses but normal MLR responses. Optimal CML responses in SLE patients did not occur at a different time point than in the normals. Plasma from most SLE patients tested did not have an effect on CML and MLR responses of normal MNC; the plasma of only one patient consistently decreased the CML of normal cells. Depletion of adherent cells from MNC of SLE patients by Sephadex G-10 fractionation allowed better CML and MLR responses. Low CML responses in patients with SLE were associated with increased disease activity and increased serum DNA binding. No association between MLR responses in SLE patients and any of the above parameters was detected. SLE patients not having received any cytotoxic treatment exhibited the lowest CML responses, while these under treatment or treated in the past had higher, although not normal, responses. MLR responses were not affected by the treatment status of the patients.