Effect of intravenous cyclophosphamide in systemic lupus erythematosus: relation to lymphocyte subsets and activation markers.

Since the mechanism mediating the beneficial effect of intravenous cyclophosphamide (IVCY) in systemic lupus erythematosus (SLE) is unknown, we investigated lymphocyte subsets and markers of activated lymphocytes in patients received IVCY, and compared the results with the effect of steroid pulse. In 55 patients with SLE, 34 patients receiving IVCY [21 cases (61.8%) were responsive] and 25 patients received steroid pulse [21 cases (84.0%) were responsive] (four patients who were resistant to steroid pulse therapy were transferred to IVCY). When the lymphocyte subsets and markers of activated lymphocytes were compared in the responsive and unresponsive group of IVCY, soluble CD4 levels and the ratio of HLA-DP-positive T cells were significantly higher in the unresponsive group. Further, the changes of these markers and costimulatory molecules [LFA-1 (CD11a), ICAM-1 (CD54), CD40 and CD40-ligand (CD154)] were also examined in the responsive patients. The ratio of HLA-DP-positive T cells did not change in the IVCY-responsive group, while it decreased in the steroid pulse therapy-responsive group. The ratio of CD11a on T cells increased and CD54 on B cells decreased in the IVCY-responsive group. The ratio of CD154 on T cells increased in the steroid pulse-responsive group, while it decreased in the IVCY-responsive group. These results suggest that the effect of IVCY is different to that of steroid pulse therapy and mainly related to B cell activation, and that these markers may contribute to predict the responsiveness of IVCY.