Prolactin in autoimmunity and antitumor defence

Prolactin (PRL) enhances inflammatory and antitumor responses in vitro and thus exhibits Th1-type cytokine-like effects. Evidence from experimental mo dels indicates that inhibition of PRL release by bromocriptine downregulate s immune reactions and ameliorates autoimmune diseases in which Th1 respons es are predominant. A direct effect of locally produced PRL in some Th1 dis eases, such as rheumatoid arthritis, supports this concept. Paradoxically, however, hyperprolactinemia can also be associated with conditions such as pregnancy, where remission of Th1-mediated diseases is known to occur in th e context of a Th2-dominated milieu. This reversal of the Th1-promoting eff ect of PRL may be due to major changes in the levels of other hormones that can annul and/or override the PRL-mediated proinflammatory state. Neverthe less, PRL, as an immunopotentiating agent, may have a powerful therapeutic role in cancer and other immunocompromised patients. (C) 2000 Elsevier Scie nce B.V. All rights reserved.