In vitro spontaneous and UVB-induced lymphocyte apoptosis are not specific to SLE

We studied in vitro spontaneous and ultraviolet light (UV)-induced lymphocyte apoptosis in patients with systemic lupus erythematosus (SLE, n = 11), cutaneous lupus erythematosus (CLE, n = 8), and other collagen diseases (n = 6), as well as normal individuals (n = 6). Apoptosis was confirmed by the presence of a 180 bp DNA ladder on gel electrophoresis. UVB-induced apoptosis was observed in 4 of 11 patients with SLE (36.3%), 3 of 8 patients with CLE (37.5%) and 2 of 6 patients (33.3%) with other collagen diseases. There was no clinical correlation between clinical photosensitivity and UV-induced apoptosis. Similarly, spontaneous apoptosis was also found in lymphocytes from patients with diseases other than SLE. No apoptosis was found in normal subjects with or without UVB irradiation (25 mJ/cm2). These data suggest that UV-induced lymphocyte apoptosis may not be specific to SLE but may be common in collagen diseases.