Symposium: Cellular Immunity and the Immunotherapy of Cancer: Tolerance and Activation: PDF OnlySchieven Gary L.; Ledbetter, Jeffrey A.Journal of Immunotherapy with Emphasis on Tumor Immunology: October 1993 Buy Abstract Summary Ultraviolet (UV) irradiation is known to suppress normal lymphocyte function, which allows UV phototherapy for a variety of applications. Although UV radiation is well known to cause DNA damage, recent findings indicate that UV irradiation can activate cellular signal-transduction processes. We have previously found that UV induces tyrosine phosphorylation in lymphocytes in a dose- and wavelength-dependent manner and also induces Ca2+ signals in Jurkat T cells via tyrosine phosphorylation of PLCγ1 and associated proteins. In this study, normal human lymphocyte subsets were examined for UV-induced Ca2+ responses. CD4+ and CD8+ T cells gave strong responses, whereas other cells did not. Although B cells did not have substantial Ca2+ signals, the pattern of UV-induced tyrosine phosphorylation was very similar to that observed after surface immunoglobulin cross-linking. We propose that the inhibitory effect of UV on lymphocyte function may be due in part to an active induction of tyrosine phosphorylation and Ca2+ signals by a process that bypasses normal receptor control. © Lippincott-Raven Publishers.