“Tolerance” in Postpartum Female Mice Induced by Strain-Specific Matings2

Abstract

The resistance of BALB/c female mice to a transplanted tumor and their ability to manifest induced resistance were changed in the direction of “tolerance” as a result of previous matings to males genetically related to the tumor. A tumor of DBA/2 origin grew in a higher percentage of postpartum females that were parous by DBA/2 males than in those parous by BALB/c males or in virgins. When postpartum or virgin females were “immunized” with DBA/2 blood prior to implantation of the tumor, the tumor grew only in females parous by DBA/2 males. This effect was observed only when the breeding male and the tumor corresponded genetically, and was more pronounced in multiparous than in primiparous females. The presence or absence of the mammary-tumor milk agent in the male had no observable influence.