Photopheresis treatment enhances CD95 (fas) expression in circulating lymphocytes of patients with systemic sclerosis and induces apoptosis

We investigated the effects of photopheresis in systemic sclerosis by analysing its influence on lymphocytes with regard to apoptosis and expression of bcl-2 and fas. Peripheral blood lymphocytes isolated immediately before and 24 h after photopheresis were investigated for apoptosis, bcl-2 and fas expression by fluorocytometry, and compared to controls. In addition, leucocytes from systemic sclerosis patients taken directly from the photopheresis system were tested for apoptosis after 24 h in culture. fas expression was similar in controls and patients with systemic sclerosis just before photopheresis, but increased 24 h after photopheresis, mainly due to an increase of CD4+CD95+ cells. bcl-2 was overexpressed in scleroderma peripheral lymphocytes, but not influenced by photopheresis. As compared to healthy controls, the percentage of apoptotic cells 24 h after photopheresis was high in cultured lymphocytes, but not ex vivo. The significant increase in fas on peripheral lymphocytes observed in this study may be a major operative mechanism of photopheresis in addition to (and possibly related to) the induction of apoptosis.