Anti-inflammatory effects of UV-irradiated lymphocytes: induction of IL-1Ra upon phagocytosis by monocyte/macrophages

One of the mechanisms proposed to explain immunomodulatory actions of ultraviolet light (UV) is production of endogenous anti-inflammatory cytokines. The purpose of the present study is to evaluate how UV light affects the production of IL-10 and IL-1Ra and to provide insight as to the role of phagocytosis of apoptotic lymphocytes in this process. ne production was evaluated in a coculture system consisting in UV-treated lymphocytes in the presence of autologous PBMC. The impact of phagocytosis was tested by two blocking agents cytochalasin E and anti-CD36 mAb. optotic process affecting irradiated lymphocytes was progressive, culminating at 48 h. To achieve significant cytokine production, irradiated lymphocytes were incubated overnight at 37°C. Coculture of apoptotic lymphocytes with autologous PBMC resulted in a significant increase of IL-1Ra mRNA (+340%; P = 0.001) and protein (+72%; P = 0.001) production. This synthesis was blocked by cytochalasin E but upregulated by CD36 receptor cross-linking. udy shows that UV light induces lymphocyte apoptosis followed by its phagocytosis by monocyte/macrophages, a step that preferentially activates IL-1Ra.