Immune capacity of mice tolerating a weakly incompatible skin allograft. I. Tolerance induction by neonatal skin graft in adult recipients or by neonatal inoculation of adult cells.

An analysis was made of the so-called "tolergenic" effect of neonatal skin grafts which tend to survive longer than control adult grafts and confer this tendency also on simultaneously transplanted adult grafts of the same genotype. When the time interval between the neonatal and adult grafts varied from zero to 150 days, it could be demonstrated that neonatal skin grafts are capable of inducing second-set response comparable to that induced by adult grafts provided that the adult graft is not given simultaneously but only following 20 days or later. Signs of immune erises (i.e. various degrees of a round-cell infiltration) were, however, detected histologically even with shorter intervals of time. The involvement of some non-specific components in the early postgrafting period was indicated by a similar effect of sera from recipients of syngeneic grafts and MSA-incompatible grafts on the survival of grafts across the male-specific antigen barrier. Only long surviving allografts tend to specifically reduce the recipient's immune responsiveness. The possible mechanisms of the specific and non-specific components in the effect of neonatal skin grafts and the factor of time are discussed.