INFLUENCE OF PLASMA PROLACTIN CONCENTRATIONS AND AGE ON NEONATAL IMMUNE FUNCTION

Prolactin (PRL) plays an immunomodulatory role in adult animals. Howev er, little information is available concerning PRL's effects on neonat al immune function. Experiments were designed to evaluate the effects of hyper-and hypoprolactinemia and age on immunity in neonatal pigs. I n Experiment 1, di-day-old pigs were treated with bromocriptine, an in hibitor of PRL release or vehicle for 1, 2, or 3 weeks. Mitogen-induce d lymphocyte proliferation was evaluated in splenic lymphocytes at 11, 18, and 25 days of age. In Experiment 2, PRL or vehicle were administ ered to 6-day-old pigs for 2 weeks and lymphocyte proliferation, in vi tro interleukin 2 (IL-2) and plaque forming cell (PFC) assays were per formed. Bromocriptine administration suppressed (P = .0001) plasma PRL concentrations and enhanced concanavalin A-(ConA) and pokeweed mitoge n-(PWM) stimulated proliferation of lymphocytes (P = .09). In contrast , PRL administration increased circulating plasma PRL concentrations ( P < .03), decreased lymphocyte proliferation (P = .08) and suppressed the numbers of PFC/mg DNA (3.5 +/- 1.6) vs control pigs (8.7 +/- 3.3). Both in vitro IL-2 production and PWM-induced proliferation was decre ased (P = .0004 and P = .002, respectively) in older vs younger pigs. The results of these studies suggest that PRL may limit specific aspec ts of immune system function;in neonatal pigs. (C) 1997 Elsevier Scien ce Inc.