Familial imprinting determines H-2 selective mating preferences.

Inbred male mice typically prefer to mate with females of a different, non-self H-2 haplotype. To determine whether this natural preference is irrevocable or results from familial imprinting, a test system was used which relied on previous observations that B6 males (H-2b) mate preferentially with congenic B6-H-2k rather than B6 females, and B6-H-2k males with B6 females. This preference was reversed in B6 males fostered by B6-H-2k parents and in B6-H-2k males fostered by B6 parents, preference in these cases favoring the same H-2 type. Thus, H-2 selective mating preference is acquired by imprinting on familial H-2 types.

Influence of a genetic difference confined to mutation of H-2K on the incidence of pregnancy block in mice.

In mice, pregnancy is often terminated when the stud male is removed and the pregnant female is exposed to the presence or scent of an unfamiliar male. It is reported here that the incidence of such blocking of pregnancy was higher when the stud and unfamiliar male differed by mutation of the H-2K class I gene of the major histocompatibility complex than when the stud and unfamiliar males were genetically identical. Thus, the olfactory distinction of mice differing by mutation of the H-2K gene, previously demonstrated after training of mice in a Y maze, can spontaneously influence neuroendocrine communications affecting reproduction.