The influence of foster nursing on the survival and immunologic competence of mice and rats.

A series of experiments were undertaken in mice and rats to confirm the report that foster nursing rats of one strain, on mothers of a different strain, can influence their survival and immunologic competence as a consequence of their receiving a significant number of immunologically competent leukocytes via the milk. These experiments have included foster nursing mice and rats, either immediately after birth, or when 25 to 36 hr old, on H-2 incompatible and Ag-B compatible and incompatible mothers, respectively, and challenging them with ear skin grafts of the same genotype as their surrogate mother. They also have included fostering animals rendered tolerant of their surrogate mother's transplantation antigens. In no instance was any evidence obtained that foster nursing can prejudice the survival or influence the immunologic competence of mice or rats.