Prolonged Survival of Skin Homograffs in Parous Female Mice

Abstract

The survival of DBA/2 skin homografts was prolonged on postpartum BALB/c female mice parous by DBA/2 males. Survival increased with multiparity through 3 litters, but no additional increase was seen with females that had 4 or more litters. Graft survival was not prolonged on virgins or females parous by intrastrain matings. In this test system, the tolerance induced by parity appeared partial or incomplete because no permanently surviving grafts were observed among 185 test animals. After BALB/c females rejected a homograft of DBA/2 skin, their resistance to a DBA/2 tumor was tested. Normal BALB/c mice can be readily immunized against this tumor by prior inoculation of blood. As expected, the 2 control groups were immunized by the skin and no tumors grew. However, in most of those parous by DBA/2 males some degree of tolerance persisted, as evidenced by growth of the tumor. No indication of maternal immunization by the hybrid fetus was observed.