Anti-major histocompatibility complex class II treatment prevents graft rejection in the hamster-to-rat cardiac xenograft

Xenografts of MHC-Deficient Mouse Embryonic Mesencephalon Improve Behavioral Recovery in Hemiparkinsonian Rats

The limited availability of human embryonic tissue for dopamine cell transplants in Parkinson's patients has led to an increased interest in using xenogeneic donor tissue. Unfortunately, without aggressive immunosup-pression, such brain xenografts are rejected by the host immune system. Chronic brain xenograft rejection is largely mediated by helper T cells, which require presentation of xenoantigens by major histocompatability complex (MHC) class II for their activation. We examined survival and function of xenografts of E13 mouse mesencephalon deficient in either MHC class I, class II, or both after transplantation into adult hemiparkinsonian rats without immunosuppression. Recipients received grafts from C57BL/6 mice that were either: 1) wild-type (wt), 2) MHC class I knockout (KO), 3) MHC class II KO, 4) MHC class I and II double KO, or 5) saline sham transplants. At 6 weeks after transplantation, recipients of MHC class I KO, class II KO, and double KO xenografts significantly reduced methamphetamine-induced circling rate while rats with wt xenografts and sham-operated rats showed no improvement. MHC class II KO grafts had the greatest number of surviving dopamine neurons. All transplants, including saline sham controls, contained infiltrating host MHC class II-positive cells. Saline sham grafts and MHC class II KO xenografts contained significantly fewer infiltrating host MHC class II-positive cells than did wt grafts. Our results show that MHC class II-deficient xenografts survive transplantation for at least 6 weeks in the absence of immunosup-pression, reduce rotational asymmetry, and provoke lesser immune reaction than wt grafts.

Anti-class II -DR humanized monoclonal antibody, IMMU-114, blocks allogeneic immune response

BACKGROUND

The effect of a humanized anti-human leukocyte antigen-DR monoclonal antibody, IMMU-114, on the allogeneic immune response was investigated in vitro.

METHODS

Responder peripheral blood mononuclear cells were cocultured with inactivated self or allogeneic stimulator peripheral blood mononuclear cells in the presence of control antibody or IMMU-114. Thymidine incorporation rates were then measured. Phenotypic changes in peripheral blood mononuclear cells and the intracellular Th1-type cytokines interleukin-2, interferon-γ, and tumor necrosis factor-α were analyzed using flow cytometry. The concentrations of interleukin-2, interferon-γ, and tumor necrosis factor-α in the mixed lymphocyte reaction culture medium were measured.

RESULTS

Thymidine incorporation rates at a 1:1 responder/stimulator ratio of allogeneic, allogeneic + IMMU-114, self, and self + IMMU-114 were 22,080.7 ± 602.4, 2,254.5 ± 118.1, 1,284.0 ± 227.8, and 494.5 ± 27.5 cpm, respectively (P = .038). IMMU-114 decreased the frequencies of human leukocyte antigen-DR-expressing CD16+56+ NK cells, CD19+ B cells, and CD3+25+ activated T cells.

CONCLUSION

Intracellular cytokine assay and measurement of Th1-type cytokines in the mixed lymphocyte reaction culture medium revealed that IMMU-114 significantly decreased the titers of interleukin-2, interferon-γ, and tumor necrosis factor-α. IMMU-114 significantly suppresses the allogeneic immune response in vitro, partly through inhibition of the Th1 response.

Impact of vaccine therapy using nuclear histone H1 on allograft survival in experimental organ transplantation

BACKGROUND

We recently reported that autoreactive antibody (Ab) against nuclear histone H1 had been identified as an immunosuppressive factor in a rat tolerogenic orthotopic liver transplantation (OLT) model. The present study aimed to determine whether the up-regulation of antihistone H1 Ab by histone H1 vaccination leads to tolerance.

METHODS

Histone H1-immunized rats were established by intraperitoneal vaccination with histone H1 at every two-weekly interval. By using mixed lymphocyte reaction (MLR) and heterotopic heart transplantation (HHT), the alloreactive T cell response and allograft survival of histone H1-immunized rats were compared with those of control rats. Cytokine and cellular profiles in histone H1-immunized rats were determined by reverse transcriptase polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and flow cytometry.

RESULTS

Immunization with histone H1 in Freund's adjuvant induced alloreactive T cell unresponsiveness and prolonged heterotopic heart allograft survival. It also down-regulated the expression of major histocompatibility complex (MHC) class II and CD25 on splenic cells, elevated the T helper cell type 2 (Th2) skewing index (Interleukin (IL)-4/interferon (IFN)-gamma ratio or IL-4/IL-2 ratio) and modified the serum cytokine profiles.

CONCLUSIONS

The present results suggest that histone H1 vaccination of transplant recipients, which leads to the production of immunosuppressive factor and the modification of the cytokine/cellular profiles, has great potential as a tolerance therapy for prospective transplantation.

Treatment with anti-MHC-class-II antibody postpones kidney allograft rejection in primates but increases the risk of CMV activation

Treatment of kidney graft recipients with antibodies that may specifically suppress the anti-donor response would be an ideal situation to prevent graft rejection. MHC class-II-specific antibodies and, in particular, DR specific antibodies have often been proposed as treatment to prevent antigen presentation, and thus graft destruction. Here we report an attempt to prevent graft rejection using a humanized MHC class-II-specific monoclonal antibody CDP855 in a cynomolgus monkey kidney graft model. A modest delay in graft rejection was observed when the antibody was given only on days 0, 1 and 2 after transplantation. Unexpectedly 50% of the animals succumbed of a viral infection, most likely CMV in two of three cases, prior to graft rejection in the first week post-transplantation. We speculate that the antibody treatment triggered CMV activation, possibly as a consequence of the activation of factors such as NF-kappab by the interaction of the antibody and its target cells.