EFFECTS OF ULTRAVIOLET-B IRRADIATION ON CELL-CELL INTERACTION - IMPLICATION OF MORPHOLOGICAL-CHANGES AND ACTIN-FILAMENTS IN IRRADIATED-CELLS

We studied the effects of ultraviolet B (UV-B) irradiation on cell-cel l interactions using mouse lymphoma RMA cells and T cell hybridoma HTB -176.10 cells. RMA cells act as stimulators by presenting H-2K(b) surf ace antigens to HTB-176.10 cells, inducing IL-2 production in HTB-176. 10 cells. Irradiating RMA cells with 1000 J/m(2) UV-B suppressed cell cluster formation between RMA and HTB-176.10 cells and reduced the lev el of IL-2 production in HTB-176.10 cells, although H-2K(b) surface an tigens of RMA cells were still expressed. Electron microscopic observa tions of irradiated RMA cells revealed that UV-B irradiation damaged c ell structures, resulting in the disappearance of microvilli on the ce ll surface, destruction of mitochondria, vacuolation of cytoplasm and swelling of the perinuclear cisterna space. We found that these altera tions were accompanied by polymerization of filamentous actin quantifi ed by flow cytometry after NBD-phallacidin staining. Our results sugge st that a target of UV-B-induced alterations is actin filaments, which support the cell morphology as the cytoskeleton, and that modificatio n of filamentous actin inhibits interaction between RMA and HTB-176.10 cells. This underlying mechanism may account for the impaired interac tion between antigen-presenting cells and T cells after transfusion wi th UV-B-irradiated allogeneic blood components.