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 ill this process. Cytokine 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 ailti-CD36 rnAb. The apoptotic process affecting irradiated lymphocytes was progressive, culminating at 48 It. To achieve significant cytokine production, irradiated lymphocytes were incubated overnight at 37degreesC. Coculture of apoptotic lymphocytes with autologous PBMC resulted in a significant increase of IL-1Ra rnRNA (+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. Our study shows that UV light induces lymphocyte apoptosis followed by its phagocytosis by monocyte/macrophages, a step that preferentially activates IL-1Ra. (C) 2004 Elsevier Inc. All rights reserved.