Influence of gamma irradiation on phenotype and function of human dendritic cells in vitro

To determine whether gamma irradiation influences phenotype and function of human dendritic cells (DC) in vitro, dendritic cells were induced from the peripheral blood mononuclear cells of multiple sclerosis patients with RPMI 1640 medium containing recombinant human GM-CSF (rhGM-CSF, 800 U/ml) and recombinant human IL-4 (rhIL-4, 500 U/ml). Phenotypic changes were monitored by light microscopy. Lipopolysaccharide at a concentration of 5 micro g/ml was added into the cultures after 6 days of growth for DC complete maturation, and the cells were cultured for another 24 hours. The harvested DC on day 7 were divided equally into several parts. One part was used as non-irradiated DC (naive DC) while the other parts were irradiated by gamma ray at a dose of 25 Gy and 30 Gy respectively. Cell surface molecules were analyzed by flow cytometry. The capability of DC to stimulated autologous T cell proliferation were determined. The results showed that gamma irradiation reduced expression of CD86, CD80 and HLA-DR molecules on dendritic cells, especially CD86 molecules. Dendritic cells effectively stimulated autologous T cells proliferation while irradiated DC in all groups showed profound decrease of capability to promote T cells proliferation. It is concluded that gamma irradiation of dendritic cells not only influenced phenotype of DC but also altered their function as stimulator cells in mixed lymphocyte reaction.