In vitro modulation of macrophage functions by 1,1-dimethylhydrazine (UDMH): Possible mechanism for UDMH-induced immuno-enhancement

Evaluation of murine lymphocyte membrane potential, intracellular free calcium, and interleukin-2 receptor expression upon exposure to 1,1-dimethylhydrazine

The effects of 1,1-dimethylhydrazine (UDMH) on several early events associated with lymphocyte activation were examined. The concentration of intracellular calcium ([Ca2+]i) and membrane potential of murine lymphocytes were found to be altered upon exposure to UDMH; [Ca2+]i was increased in murine thymocytes, while splenocytes exhibited membrane hyperpolarization. In addition, interleukin-2 receptor expression induced by in-vitro concanavalin A stimulation of murine splenocytes at 24 and 48 h in the presence of UDMH was not affected. UDMH may interfere with the ability of these two distinct lymphocyte populations to regulate normal ionic fluctuations, thus contributing to altered immune responsiveness.

Effect of 1,1-dimethylhydrazine (UDMH) on Corynebacterium parvum-associated immunosuppression in mice

These studies further investigate the immunoenhancement properties of UDMH by utilizing Corynebacterium parvum-induced immunosuppressed mice as well as evaluating activated macrophage production of reactive oxygen intermediates or their effects. Forty-eight hour Con A-induced lymphoblastogenic responses from splenocytes isolated from C. parvum and UDMH-treated Balb/C mice were significantly increased compared with C. parvum alone, although less than normal control mice (no treatment). In vitro bioassay of IL-2 production in cell culture supernatant isolated from these same treatment groups exhibited a pattern of stimulation similar to that of lymphocyte blastogenesis. In addition, UDMH did not interfere with H2O2-mediated suppression of either Con A- or LPS-induced lymphocyte blastogenesis and actually enhanced suppression of Con A-induced lymphocyte cultures at 25 micrograms/ml. We also report that production of superoxide anion from TPA-activated peritoneal macrophages exposed to various concentrations of UDMH in vitro was not affected. Although in vivo exposure to UDMH partially reversed C. parvum-induced immunosuppression in mice, the exact mechanism by which UDMH acts to reverse this immune suppression is not clear. UDMH does not appear to interfere with either activated peritoneal macrophage production of superoxide anion or H2O2-induced suppression of lymphocyte blastogenesis to elicit immune enhancement.