Estrogenic xenobiotics affect the intracellular activation signal in mitogen-induced human peripheral blood lymphocytes: immunotoxicological impact.

The present study was an attempt to elucidate the effect of estrogenic xenobiotics on the proliferation of mitogen-stimulated human peripheral blood lymphocyte (PBL). Our findings follow: (a) the proliferation of PBL in response to phytohemagglutinin (PHA) was mediated by protein kinase C activity, but estrogenic xenobiotics had a strong inhibitory effect on protein kinase C activity of PHA-stimulated PBL; (b) cytoplasmic extracts from PHA-stimulated PBL greatly activated DNA replication, but estrogenic xenobiotics had a strong inhibitory effect on these activities. The results suggest that the cytoplasmic signal-generating system in mitogen-treated PBL is inhibited by estrogenic xenobiotics, and that the defect occurs at all stages in the sequence of events leading to DNA synthesis and cell proliferation.