Lymphocyte alterations after prolonged sunlight exposure.

BACKGROUND It has been suggested that prolonged exposure to sunlight may induce systemic or local immune alterations, which may facilitate the development of skin cancer and, perhaps, non-Hodgkin's lymphona. The effects of prolonged sunlight exposure on peripheral blood cells were studied. METHODS Leukocytes and lymphocyte subpopulations of 12 volunteers aged 10-45 were investigated before and after a 3-week summer holiday in seaside resorts in Greece. Lymphocyte phenotypes were estimated using monoclonal antibodies and flow cytometry. RESULTS There were no significant differences with respect to total numbers of T cells, T-helper/inducer, T-suppressor/cytotoxic, B cells or HLA-Dr+ cells. However, we have found evidence of lymphocyte stimulation, reflected in an increase in cells expressing the interleukin-2 receptor (IL-2R) and, more specifically, an increase in the T cells expressing IL-2R and HLA-Dr antigens. An increase in natural killer cells has also been noticed. CONCLUSIONS These findings suggest that prolonged intense exposure to sunlight may be associated with immunostimulation, rather than immunosuppression.