Meeting Abstract

P3.34  Saturday, Jan. 5  Melatonin organizes the immune system of Siberian hamsters MARTIN, LB*; WEIL, ZM; NAVARA, KJ; TUTHILL, C; ZUCKER, I; NELSON, RJ; University of South Florida; Ohio State University; University of Georgia; University of California, Berkeley; University of California, Berkeley; Ohio State University lmartin@cas.usf.edu

Many temperate vertebrates exhibit seasonal changes in phenotypic traits. Increased nocturnal durations of the pineal-derived hormone, melatonin, in short day-lengths directly facilitates many seasonal adjustments in physiology, including immune function. Melatonin can exert both organizational and activational effects on phenotypic traits, although organizational effects on immune function have yet to be considered. Whereas pinealectomy and continuous light exposure can affect immune responses in Siberian hamsters (Phodopus sungorus), whether and to what extent melatonin exposure during development affects immune activity in adulthood is unknown. To assess potential organizational effects of melatonin on the immune system, nulliparous female Siberian hamsters were either pinealectomized or sham-pinealectomized then impregnated by intact males. Male and female offspring were then pinealectomized (or sham-pinealectomized) at 3d of age, and once all individuals reached adulthood, multiple aspects of immunity were measured. Melatonin had strong organizational effects on immunity although effects were not sex-specific. Maternal pinealectomy effectively abolished delayed-type hypersensitivity (an index of T-cell mediated inflammation), but ability to generate antibodies against a novel protein (an index of B-cell mediated immunity) and phagocytic capacity of peritoneal macrophages were greater compared to offspring from pineal-intact dams. Pineal status of pups had comparatively minimal effects on immune responses in adulthood. These data indicate that maternal melatonin has extensive organizational effects on the immune system of Siberian hamsters, which may allow females to bias the immune systems of their offspring in directions conducive to the time of year in which they are born.