Resistance of neonatal tolerance in mice to abrogation by normal immunocytes

The mechanisms of neonatally induced tolerance in CAF₁ mice to bovine serum albumin were investigated with cell transfer experiments and primary interaction between radiolabeled antigen and antisera for antibody measurements. Adoptive transfer of normal syngeneic splenocytes, of thymocytes, or of thymus-bone marrow cell combinations did not break this tolerance though proved effective for breaking irradiation-caused tolerance. Similar transfer of spleen cells taken from immunized mice did abrogate neonatal tolerance; but spleen cells transferred from immunized mice that subsequently also had been desensitized did not, even though they could provide nontolerant recipients with anamnestic responses. Neither allogeneic nor xenogeneic spleen cells broke the tolerance.Thus, the neonatal tolerance studied appears to suppress primary immunologic response but not an anamnestic response. It appears more likely to be an active suppressive phenomenon than one of clone loss.