Human‐mouse lymphoid chimeras: host‐vs.‐graft and graft‐vs.‐host reactions

Human peripheral blood lymphocytes (huPBL) were injected into mice with severe combined immune deficiency (SCID). It was ascertained that murine natural killer (NK) cellswere capable of affecting engraftment of human lymphocytesin SCID mice. The presence of host NK cells resulted in the clearance of the human lymphocytes. Human T lymphocyteswere the primary cell to engraft in the SCID recipients, with human T cells being detected in the spleen, lymph nodes, bone marrow and peritoneal cavity of the mice up to several months after transfer. No human T cells were detected in the murine thymus and thelevel of engraftment in the periphery could be highly variable. Additionally, there appeared to be significant reactions between the human lymphocytes and the murine host resulting in a xenogeneic graft‐vs.‐host reaction (XGVHR). The predominant manifestation involved splenomegaly resulting from an expansion of murine hematopoietic cells in the spleens of these xenogeneic chimeras. The severity of the XGVHR could be correlated with the extent of human T cell engraftment and the recovered human Tcells were found to be in a proliferative state. Thus, there appear to be significant host‐vs.‐graft and graft‐vs.‐host interactionsoccurring in human/mouse lymphocyte chimeras.