Ontogenetic aspects of sexual dimorphism and the primary immune response to sheep erythrocytes in hamsters from prepuberty through senescence.

Ontogeny of the primary response to sheep erythrocytes of age-matched groups of male and female hamsters was studied at various chronological ages ranging from prepuberty to senescence. Selected organs were likewise weighed upon sacrifice to obtain developmental patterns. Adrenal weights were higher in the male, and pituitary weights were higher in the female; for both organs typical dimorphism was demonstrable by 36 days. Spleen weight and index favored the female by 46 days. Immunological sex dimorphism first appeared in groups injected at 53 days and autopsied at 58 days and persisted through senescence. Sexual dimorphism of antibody-mediated immunity, previously shown to favor the female in both the primary and secondary immune responses, thus follows the dimorphism of total amount of splenic lymphoid tissue and occurs shortly after realization of sexual maturity in the male. These findings support our previous suggestion of the suppressive effect of androgens on the antibody-mediated immune responsiveness of the male hamster.