NEONATAL TOLERANCE TO ALLOANTIGENS IS INDUCED BY ENRICHED ANTIGEN-PRESENTING CELLS

Spleen and bone marrow cells from normal or Rag-1-deficient donors are equally competent in their ability to induce neonatal transplantation tolerance in semi-allogeneic hosts, and the latter are also capable o f tolerizing fully allogeneic recipients. Both types of donor cells re sulted in comparable levels of haemopoietic chimerism in tolerant anim als. Lymphoid hyperactivity, however, was absent in animals tolerized with Rag-1-deficient cells. The authors conclude that reonatal toleran ce induced with haemopoietic cells requires no donor lymphocytes, and is thus not the result of deficient antigen presentation. Furthermore, the state of tolerance can be dissociated from the lymphoid hyperacti vity that requires donor lymphocytes and is regularly scored in conven tionally tolerized animals.