Depression of Con A proliferative response of immune cells by in vitro hyperoxic exposure--protective effects of thiol compounds.

Time dependent response for hyperoxic exposure was determined in vitro on ConA proliferative response of rat splenocytes, peripheral blood mononuclear cells and thymocytes. The proliferative responses were evaluated after different lengths of hyperoxic exposure (12-72 h, FiO2 = 0.95). After 24 h oxygen exposure, the spleen cell viability assessed by dye exclusion was normal but DNA synthesis was markedly suppressed in the above three types of cells. Total or partial protection of the mitogenic response to ConA was obtained by 2-mercaptoethanol, reduced glutathione or L-cysteine addition in culture medium; only selenomethionine had no protective effect. Thymic cells showed a different response-curve: after 6 h exposure to normobaric oxygen DNA synthesis was decreased and was not restored by any of the thiol compounds tested. In this respect, these cells demonstrated different susceptibility to an oxidant injury, i.e. exposure to high oxygen concentration. From a pharmacological point of view O2 exposure and altered immune response could be proposed as a useful model for screening the antioxidant drug activity.