Engraftment of human T, B and NK cells in CB.17 SCID/beige mice by transfer of human spleen cells.

Models of severe combined immuno-deficient (SCID) mice reconstituted with a competent human immune system represent a valuable tool for the study of human immune responses in vivo. Reconstitution with human cells can be achieved using large numbers of peripheral blood lymphocytes, but levels of engraftment are poor and graft versus host disease (GVHD) frequently occurs. SCID/beige mice are at the same time deficient for adaptive and innate immunity and the objective of this study was to develop a safe and efficient way to achieve human lymphocyte engraftment in these mice using human spleen cells. After institutional authorisations and informed consent of relatives, a piece of spleen was obtained from cadaveric organ donors and the splenocytes were isolated and cryopreserved for later use. Single intraperitoneal injections of 5-100 x10(6) splenocytes were performed into SCID/beige mice. Reconstitution of a human immune system was monitored weekly by the presence of human cells and IgG in peripheral blood. The mice were sacrificed 4 weeks after the injection and the engraftment in lymphoid organs was studied. A reproducible reconstitution was obtained with intraperitoneal injection of 30-40 x10(6) spleen cells. Human T, B and NK cells as well as human IgG were present in peripheral blood. In lymphoid tissues, the same lymphocytic subpopulations were detected and in addition some antigen presenting cells. The reconstitution was functional because graft rejection was observed after transplantation of human allogeneic tissues. When less than 30 x10(6) cells were injected, the reconstitution was variable. When more than 40 x10(6) cells were injected, GVHD occurred with increasing frequency. In conclusion, we show that intraperitoneal injection of 30-40 x10(6) human splenocytes into SCID/beige mice induces a quick and functional engraftment of human T, B and NK cells with no risk of GVHD. This model may be used to study human transplantation immunobiology in vivo.