Lymphocyte apoptosis in systemic lupus erythematosus: relationships with Fas expression, serum soluble Fas and disease activity

Lupus specific autoantigens are exposed on apoptotic cells. The increased n umber of apoptotic lymphocytes reported in systemic lupus erythematosus (SL E) may be attributable to abnormalities of lymphocyte Fas expression or ser um soluble Fas. In the present study we analysed the count of circulating apoptotic lymphoc ytes in SLE patients (n = 50), by flow cytometry using Annexin V, compared to rheumatoid arthritis patients (RA, n = 20), inflammatory bowel disease p atients (IBD, n = 20) and normal controls (n = 20). Lymphocyte Fas expressi on and serum soluble Fas were measured and related to numbers of apoptotic lymphocytes. The percentage of apoptotic lymphocytes, determined by Annexin V binding, w as significantly increased in peripheral blood of SLE patients (median = 4. 2%) compared with normal healthy donors (median = 1.1%) and IBD patients (m edian = 2.0%) but not RA (median = 3.9%). SLE lymphocyte Fas expression was not significantly different from RA or IBD patients. Serum soluble Fas in SLE patients correlated positively with apoptotic lymphocytes and antibodie s to double stranded DNA. This study suggests that increased apoptotic lymphocytes and increased lymp hocyte Fas expression may not be specific to SLE. Serum soluble Fas may hav e a role in the regulation of lymphocyte apoptosis in SLE.