The time course of immune modulation induced by acute treatment with O,S,S-trimethyl phosphorodithioate (OSS-TMP), an impurity in technical formulations of malathion, was examined in female C57BL/6 mice. The immune parameters studied included the generation of cytotoxic T lymphocytes (CTL) to alloantigen (H-2 incompatible) and antibody secreting cells to sheep red blood cells, proliferative response to the mitogens, and interleukin-2 (IL-2) production. Acute administration of the non-toxic doses of OSS-TMP, i.e. 20 or 40 mg/kg, led to an elevation in the generation of a CTL response on day 1 or 7, respectively. At 20 mg/kg OSS-TMP, the antibody response was elevated at day 3. However, at a dose of 40 mg/kg OSS-TMP, the antibody response was suppressed at day 1 following treatment. Following acute administration of 60 or 80 mg/kg OSS-TMP, the generation of an antibody and CTL responses was suppressed at all time points tested with 1 exception. One day following treatment at a dose of 60 mg/kg OSS-TMP, there was no change in the CTL response. At day 7 following treatment, the mitogenic responses to lipopolysaccharide and phytohemagglutinin were elevated at all doses of OSS-TMP administered. At this time point, however, the proliferative response to Concanavalin A was elevated in a dose dependent manner. IL-2 production was suppressed following acute administration of 60 or 80 mg/kg OSS-TMP at all time points tested and at all doses tested on day 5 following treatment. These data indicate that OSS-TMP, unlike its congener, O,O,S-Trimethyl phosphorothioate, enhances the generation of humoral and cell mediated immune responses of C57BL/6 mice following administration of non-toxic doses.
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