Why do men produce prolactin?
Prolactin has a well-recognized gender-specific reproduction-related hormonal effect. In addition, there is a growing body of literature documenting that it also plays a proinflammatory role in various physiological and pathological settings. The presence of the prolactin receptor on immunocytes is consistent with a place for this hormone in immune system homeostasis. Numerous reports have linked prolactin to an enhanced immune response and have associated high levels of prolactin to various autoimmune diseases. This is consistent with the well-established heightened immune responses and higher prevalence of autoimmune diseases in women. However, the mechanisms by which prolactin plays a proinflammatory role are still largely elusive. In this issue, Montes de Oca et al1 (p. 633) evaluated the hypothesis that prolactin may stimulate an integrin-mediated adhesion of leukocytes to endothelial cells. Through a series of carefully constructed experiments, these authors demonstrated for the
