THYMIC EPITHELIUM INDUCES FULL TOLERANCE TO SKIN AND HEART BUT NOT TOB-LYMPHOCYTE GRAFTS

Athymic nude mice reconstituted at birth with allogeneic thymic epithe lia (TE) from day 10 embryos (E10), show life-long specific tolerance to skin and heart grafts, but eliminate B lymphocytes of the TE donor haplotype, nearly as well as those from a third strain. Previous immun izations with B cells do not alter the state of tolerance to skin graf ts, but specifically accelerate elimination of lymphocytes. In contras t, transplantation of E15 allogeneic thymuses already seeded by hemato poietic cells resulted in chimeras tolerant to both skin and B lymphoc ytes. In vitro reactivities towards stimulator spleen cells of the hap lotype of the thymus were observed in both E10 TE and E15 thymus chime ras. We conclude that induction of full in vivo tolerance to B cells r equires hematopoietic cells,while this is not the case for induction o f tolerance to skin and heart tissues; furthermore, in vitro reactivit y to stimulator spleen cells of the tolerized haplotype is independent of in vivo tolerance.