KINETICS AND REPERTOIRE SELECTION OF T-CELLS DERIVED FROM THE EARLY WAVES OF FETAL THYMUS COLONIZATION AFTER THYMUS GRAFTING IN ALLOGENEIC NUDE RECIPIENTS

The survival of T cells derived from the early waves of thymus coloniz ation by haemopoietic cell precursors was investigated by grafting thy mus from B6.Thy1.1 day 14 embryos (E14) (first wave) or E17 or newborn thymus (subsequent waves) into allogeneic athymic BALB/c (Thy1.2) nud e recipients. The survival of donor-derived Thy1.1 cells was longer wh en they were derived from early thymocytes. Donor B6.Thy1.1 V beta 5 a nd V beta 11 T cells, although maturing in BALB/c host presenting M1s2 (a) superantigens, were not deleted, in contrast to host Thy1.2 T cell s differentiating from endogenous stem cells. These results show that the population of T cells derived from early precursors undergoes part icular selection characteristics, which favour the inclusion of potent ially autoreactive cells with prolonged survival, even in H-2 allogene ic conditions which normally do not allow the survival of peripheral T cells.