Newborn blood can engraft adult mice without inducing graft-versus-host disease across non H-2 antigens.

Cells derived from human cord blood were recently used instead of bone marrow (BM) for transplantation. However, several questions concerning the potential of these cells to reconstitute the hematopoietic and immunologic system of the recipient and to induce a graft-versus-host disease (GVHD) remain unanswered. Here we used newborn blood (NBB) cells from B10.D2 mice to engraft lethally irradiated (DBA/2 x B10.D2)F1 recipients incompatible for multiple non H-2 antigens. Few mature T cells were found in NBB as in adult BM and both contain around 10% to 20% SCA-1+ pluripotent progenitor cells. Yet numerous immature CD4+CD8+ TCR alpha/beta low Thy-1high T cells were present in NBB. In contrast, adult peripheral blood (PB) exhibits a mature T-cell phenotype and contains few progenitor cells. The injection of blood pooled from one to three newborn mice resulted in the engraftment of 71% to 86% of F1 recipients, which survived more than 100 days without clinical signs of GVHD. The injection of BM leads to 100% survival whereas the injection of adult PB resulted in rapid mortality, both without signs of GVHD. In NBB-engrafted F1 surviving mice, T-cell reconstitution preceded B-cell reconstitution, and the degree of donor cell chimerism increased progressively with time. Additionally, 2 to 4 months after transplantation, T cells from these mice were tolerant to host non H-2 antigens but kept reactivity against third-party Ags. Host specific tolerance in NBB-engrafted F1 mice was confirmed by in vivo transfer experiments. In conclusion, NBB cells were able to reconstitute the lymphohematopoietic system of lethally irradiated adult mice without inducing GVHD against incompatible non H-2 antigens. Thus, this experimental model in vivo may be relevant to the human cord blood transplantation.