Conversion of normal rats into scid-like animals by means of bone marrow transplantation from scid donors allows engraftment of human peripheral blood mononuclear cells

We have recently shown that lethally irradiated normal strains of mice, radioprotected with SCID bone marrow, can be engrafted with human peripheral blood mononuclear cells (PBMC). We now demonstrate that lethally irradiated Lewis rats can also be radioprotected with a transplant of SCID bone marrow cells, administered 1 day after total body irradiation. Split chimerism was found in PBMC, 30 days after transplantation, with predominance of SCID donor-type cells. The average percentages of CD4 and CD8 T cells, of mouse or rat origin, were 1 mg/ml) were initially found after 2 weeks ; these levels were similar to those found in the irradiated mouse model and in the SCID model. Likewise, marked human antitetanus response, predominantly of the IgG type, was recorded 2 weeks after the immunization, reaching maximal levels at 4 weeks. The triple-chimeric SCID-like rats, which accept as much as 1000x10 6 human PBMC, can potentially be used to elicit both antibody responses and T cell responses against specific antigens, with the advantages of a larger animal.