Evaluation of the tolerogenic effects of donor bone marrow cells using a severe combined immunodeficient mouse–human islet transplant model

Abstract

Summary The immunoregulatory role of human donor bone marrow cells (DBMC) has been studied extensively in our laboratory using in vitro and ex vivo assays. However, new experimental systems that can overcome the limitations of tissue culture assays but with more clinical relevance than purely animal experimentation, needed to be generated. Therefore we have developed a new human peripheral blood lymphocyte (PBL) severe combined immunodeficient (SCID) mouse islet transplantation model without the occurrence of graft-versus-host disease (GvHD) and have used it to evaluate the tolerogenic effects of DBMC. Nonobese diabetogenic (NOD)–SCID mice were transplanted with human deceased donor islets and were reconstituted with human PBL (allogeneic to islets; denoted as recipient) with or without DBMC from the islet donor. It was observed that the most cellularly economical dose was 3000 islets per animal and that injection into the portal vein was better than implantation under the kidney capsule. Even though maximal lymphoid reconstitution was observed with 40-million fresh and anti-CD3 activated recipient PBL (conventional method), the mice developed severe graft GvHD. However, with the new method of reconstitution where animals were injected with 20-million anti-CD3-activated plus 40-million anti– donor-activated recipient PBL, no discernible GvHD was observed. More importantly, this latter method was associated with islet transplant rejection, which in turn could be abrogated by co-injection of the animals with DBMC. These in vivo results confirmed our previous in vitro observations that human DBMC have regulatory activity.

Human allograft rejection in humanized mice: a historical perspective

“…81 A similar two-stage injection protocol of human PBMC was used in NOD-scid mice to demonstrate human islet allograft rejection. 82 In these experiments, NOD-scid mice were first transplanted with human islet allografts and then 3 days later injected with PBMC that were activated by in vitro stimulation with anti-CD3 antibody. Between 2 and 4 days later, these mice received a second injection with PBMC that had been stimulated in vitro with irradiated allogeneic splenocytes from the islet donor.…”

“…Rejection of human islet allografts was prevented by the co-injection of T cell-depleted bone marrow derived from the islet donor, suggesting that the establishment of microchimerism was sufficient to induce tolerance in this humanized model. 82 The NOD-scid mouse has also been used to study the rejection of human islet allografts after depletion of murine NK cells with a monoclonal antibody specific for CD122. 42 In this study, transplantation of human islet allografts into STZ-treated diabetic NOD-scid mice efficiently restored normoglycemia.…”