Presence of alloantigen-reactive cells in neonatally tolerized mice.

Neonatally induced fully tolerant mice possess cytotoxic effector cells, specific for the tolerizing antigens, which can be induced by polyclonal T cell activators in vivo (Con A) on in vitro (poly A:U). Therefore, clonal deletion of specific effector cells is eliminated as the mechanism by which skin grafts are retained in tolerized mice.