Suppression of cytotoxic response to histoincompatible cells. II. Analysis of the role of two independent T suppressor pools in maintenance of neonatally induced allograft tolerance in mice.

The kinetics of appearance of the precursors of SuppA cells (capable of inhibiting CTLp leads to CTL) or SuppB cells (capable of inhibiting (stem cells leads to CTLp) in neonatal mice, as well as the appearance of SuppA/SuppB cells in mice given neonatal innoculations of semiallogeneic spleen cells has been investigated. The data obtained are consistent with the idea that SuppA cells have a natural role to play in the induction of neonatal tolerance, whereas SuppB cells may be more important for the maintenance of the tolerant state. Unlike the level of SuppB cells, the level of SuppA cells in tolerant mice seems to be modulated by the presence of the tolerizing determinants. Data are provided to show that SuppB cells, once induced in tolerant mice, can adoptively transfer specific allograft unresponsiveness to newborn syngeneic mice in the absence of added tolerizing antigen, whereas SuppA cells are not able to do so. These data fit the notion that SuppB cells may be responsible for the phenotype of clonal deletion.