Evidence for immunologic immaturity of cord blood T cells. Cord blood T cells are susceptible to tolerance induction to in vitro stimulation with a superantigen.

T cell blasts resulting from stimulating human cord blood (CB) mononuclear cells (MC) and adult peripheral blood (APB) MC with a bacterial superantigen, toxic shock syndrome toxin-1 (TSST-1), and then with human rIL-2 were investigated for their reactions to restimulation with TSST-1. Expression of TCR V beta 2, which determines the potential reactivity to TSST-1 and of CD45RO, was increased in both TSST-1-induced CB and APB T cell blasts. Most preparations of the TSST-1-induced CB T cell blasts exhibited low or no production of IL-2 and IL-4 in response to restimulation with TSST-1, while the APB T cell blasts showed high responses. TSST-1-induced T cell blasts derived from APB T cells depleted of both CD45RO+ T cells and HLA class II+ T cells showed high IL-2 production in response to restimulation with TSST-1. TSST-1-induced CB T cell blasts generated in the presence of DR+ L cells with high accessory cell activity still showed a low response to restimulation with TSST-1. These results indicate that CB T cells are inherently highly susceptible to tolerance induction by bacterial superantigens, suggesting the immunologic immaturity of CB T cells.