Long survival and immunologic reconstitution following transplantation with syngeneic or allogeneic fetal liver and neonatal spleen cells.

(1)Spleen cells from newborn syngeneic and allogeneic mice that lack fully differentiated T lymphocytes can be used as a hematopoietic source to reconstitute both hematopoietic and lymphoid systems of lethally irradiated mice without producing a GVHR. (2) Fetal liver cells from syngeneic and allogeneic mice that lack postthymic T lymphocytes can also be used for hematopoietic and immunologic reconstitution of lethally irradiated mice without producing GVHR. (3) Immunologic deficiency is observed in some experiments in mice given supralethal irradiation (1000 R) and fetal liver as reconstituting hematopoietic tissue. (4) The findings suggest that Tcells, at an early stage of differentiation, are more susceptible to tolerance induction than are T lymphocytes at later stages of differentiation and do not, in general, produce GVHR. (5) It is postulated that hematopoietic cells, free of postthymic lymphoid cells, can be used for hematopoietic or immunologic reconstituting and cellular engineering without producing GVHD.