ULTRAVIOLET-RADIATION INDUCES DIFFERENTIAL CALCIUM SIGNALS IN HUMAN PERIPHERAL-BLOOD LYMPHOCYTE SUBSETS

Ultraviolet (UV) irradiation is known to suppress normal lymphocyte fu nction, which allows UV phototherapy for a variety of applications. Al though UV radiation is well known to cause DNA damage, recent findings indicate that UV irradiation can activate cellular signal-transductio n processes. We have previously found that UV induces tyrosine phospho rylation in lymphocytes in a dose- and wavelength-dependent manner and also induces Ca2+ signals in Jurkat T cells via tyrosine phosphorylat ion of PLCgamma1 and associated proteins. In this study. normal human lymphocyte subsets were examined for UV-induced Ca2+ responses. CD4+ a nd CD8+ T cells gave strong responses, whereas other cells did not. Al though B cells did not have substantial Ca2+ signals, the pattern of U V-induced tyrosine phosphorylation was very similar to that observed a fter surface immunoglobulin cross-linking. We propose that the inhibit ory effect of UV on lymphocyte function may be due in part to an activ e induction of tyrosine phosphorylation and Ca2+ signals by a process that bypasses normal receptor control.