Functional differentiation of T cell precursors. I. Parameters of carrier-specific tolerance in murine helper T cell precursors.

Irradiated mice reconstituted with bone marrow from sheep gamma-globulin- (SGG) tolerant syngeneic donors display reduced IgG responsiveness to challenge with trinitrophenylated (TNP)-SGG compared with recipients of normal marrow. This effect is SGG-specific and is due neither to suppressor T cells nor to antigen carryover. "Helper T cell precursor tolerance" can be induced with as little as 40 micrograms tolerogen (SGG). Unlike mature helper T cells, these precursors show both a rapid induction and rapid waning patterns, suggesting a high rate of turnover. Our results imply that marrow helper T cell precursors bear antigen-specific receptors and that the T cell repertoire must be at least partially generated before residence in the thymus.