Effects of Noninherited Maternal Antigens on Allotransplant Rejection in a Transgenic Mouse Model

Hematopoietic stem cell infusion/transplantation for induction of allograft tolerance

PURPOSE OF REVIEW

The present review updates the current status of basic, preclinical, and clinical research on donor hematopoietic stem cell infusion for allograft tolerance induction.

RECENT FINDINGS

Recent basic studies in mice provide evidence of significant involvement of both central deletional and peripheral regulatory mechanisms in induction and maintenance of allograft tolerance effected through a mixed chimerism approach with donor hematopoietic stem cell infusion. The presence of heterologous memory T cells in primates hampers the induction of persistent chimerism. Durable mixed chimerism, however, now has been recently induced in inbred major histocompatibility complex-mismatched swine, resulting in tolerance of vascularized composite tissue allografts. In clinical transplantation, allograft tolerance has been achieved in human leukocyte antigen-mismatched kidney transplantation after the induction of transient mixed chimerism or persistent full donor chimerism.

SUMMARY

Tolerance induction in clinical kidney transplantation has been achieved by donor hematopoietic stem cell infusion. Improving the consistency and safety of tolerance induction and extending successful protocols to other organs, and to organs from deceased donors, are critical next steps to bringing tolerance to a wider range of clinical applications.

Cellular therapies supplement: the peritoneum as an ectopic site of hematopoiesis following in utero transplantation

BACKGROUND

In utero transplantation (IUT) has the potential to treat birth defects early before full development of the immune system. Relatively small grafts, which are not matched for major histocompatibility antigens, can be delivered even before onset of disease symptoms. IUT of hematopoietic stem cells is usually performed via intraperitoneal injection, yet the fate of donor cells in the peritoneal cavity is not fully understood. We review our recent work and present new data demonstrating that the peritoneum can be a site of ectopic hematopoiesis with implications for IUT and immune tolerance induction.

STUDY DESIGN AND METHODS

Haplogeneic and allogeneic fetal transplants were performed in mice and engraftment tracked by flow cytometry. Immune tolerance was studied by mixed lymphocyte reactions and skin transplantation. Adult syngeneic murine transplants and xenogeneic human into immunodeficient mouse transplants were performed to follow hematopoietic retention in the peritoneum and engraftment of the marrow.

RESULTS

Although most transplanted cells rapidly clear the peritoneum, hematopoietic cells and cells with the phenotype of hematopoietic precursors can remain in the peritoneal cavity for months after transplant. The presence of donor cells in the peritoneum can contribute to donor-specific tolerance, but sufficient peripheral blood chimerism is required to ensure acceptance of donor skin grafts.

CONCLUSION

Ectopic hematopoiesis and the survival of stem cells in the peritoneum offer the possibility of better using the peritoneal cavity to delivery stem cells and foster the development of immune tolerance to alloantigens or other foreign antigens.

Modified ELISPOT assay may predict T-cell hyporesponsiveness to non-inherited maternal antigens

Clinical reports have suggested the existence of immunological tolerance to noninherited maternal antigens (NIMA) in human leukocyte antigen (HLA) mismatched allogeneic stem cell transplantation (allo-SCT). We studied the T-cell reactivity using IFN-gamma enzyme-linked immunospot (ELISPOT) assay in three HLA fully matched allo-SCT cases and one healthy volunteer family case. In HLA fully matched allo-SCT cases, ELISPOT assay could detect the hyporesponsiveness of T cells from donors to the B cells from recipients. Moreover, ELISPOT assay showed that the T cells from an individual responded to B cell from his mother significantly weakly than those from an unrelated HLA-haploidentical individual. These observations suggest that our IFN-gamma ELISPOT assay-based method may predict the presence of immunological tolerance to NIMA.

The influence of inherited and noninherited parental antigens on outcome after transplantation

Contact between the immune systems of mother and child during pregnancy has an impact on transplantation later in life. Exposure to inherited paternal human leukocyte antigens (HLA) (IPA) and the noninherited maternal HLA antigens (NIMA) can lead to either immunization or tolerization. Exposure to IPA seems to have a more immunizing effect as the mature immune system of a mother can form anti-HLA antibodies against the foreign paternal HLA molecules. On the other hand, exposure of a child to the NIMA antigens during pregnancy may lead to NIMA-specific tolerance. This review provides an overview of the current knowledge on the impact of this fetal-maternal interaction on the alloimmune response and clinical transplantation.