New aspects of prolactin and immunity: a lymphocyte-derived prolactin-like product and nuclear protein kinase C activation.

In addition to its growth regulating properties, new evidence reviewed here by Diane Haddock Russell demonstrates that prolactin has important immunoregulatory properties. In immune-compromised dwarf mice, prolactin restores immunocompetence. Human lymphocytes have prolactin receptors and mitogen-stimulated lymphocytes make and secrete a prolactin-like activity. Prolactin can stimulate the activation of nuclear protein kinase C in spleen and liver isolated nuclear preparations. This activation is blocked by prolactin receptor monoclonal antibody, suggesting that there is a receptor-mediated activation process in the nucleus. The discovery of the ability of prolactin and growth factors to activate nuclear protein kinase C may constitute a breakthrough in our understanding of how these hormones regulate trophic responses.