Modulation of murine lymphocyte and macrophage proliferation by parenteral zinc.

The effects of a single i.p. injection of zinc (0.7, 1.3, 4.0 or 12.0 mg/kg), 24 h prior to sacrifice, on lymphocyte blastogenesis as well as lymphocyte and macrophage progenitor cell proliferation were examined using cells from adult BALB/c mice. Splenic lymphocyte blastogenesis in response to T cell mitogens decreased for mice receiving the highest zinc dosage while responses to B cell mitogens were initially depressed, subsequently increased, and finally declined sharply as the LD50 was approached. Splenic B cell colony formation decreased linearly in relation to zinc dosage with a 50% suppression of colony formation observed at approximately 8.0 mg/kg. In contrast, bone marrow granulocyte-macrophage colonies were enhanced at higher dosages (greater than or equal to 2.5 mg/kg) of zinc. These results indicate that zinc exposure at dosages less than the LD50 can influence lymphocyte blastogenesis and clonal expansion of both B cell and macrophage progenitors.