Accommodation in ABO-incompatible kidney allografts, a novel mechanism of self-protection against antibody-mediated injury

IL-11 protects human microvascular endothelium from alloinjury in vivo by induction of survivin expression

IL-11 can reduce tissue injury in animal models of inflammation but the mechanism(s) is unknown. When C.B-17 SCID/beige mice bearing human skin grafts are injected i.p. with human PBMC allogeneic to the donor skin, infiltrating T cells destroy human microvessels by day 21. Intradermal injection of human IL-11 (500 ng/day) delays the time course of graft microvessel loss without reducing the extent of T cell infiltration. Protective actions of IL-11 are most pronounced on day 15. IL-11 has no effect on T cell activation marker, effector molecule, cytokine expression, or endothelial ICAM-1 expression. IL-11 up-regulates the expression of survivin, a cytoprotective protein, in graft keratinocytes and endothelial cells. Topical application of survivin antisense oligonucleotide down-regulates survivin expression in both cell types and largely abrogates the protective effect of IL-11. We conclude that in this human transplant model, IL-11 exerts a cytoprotective rather than anti-inflammatory or immunomodulatory effect mediated through induction of survivin.

Plasma exchange conditioning for ABO-incompatible renal transplantation

The supply of deceased donor kidneys is inadequate to meet demand. To expand the pool of potential donors, ABO-incompatible transplants from living donors have been performed. We present the Mayo Clinic experience with such transplants. Enrollment was open to patients when the only available potential living kidney donor was ABO-incompatible. Conditioning consisted of plasma exchanges followed by intravenous immunoglobulin. Splenectomy was performed at the time of transplant surgery. Post-transplant immunosuppression consisted of anti-T lymphocyte antibody, tacrolimus, mycophenolate mofetil, and prednisone. Isoagglutinin titers and scores were determined before and after each plasma exchange. Transplant outcomes were determined. Twenty-six ABO-incompatible transplants were performed. No hyperacute rejection occurred. Mean patient follow-up was 400 days. Patient and graft survivals at last follow-up were 92 and 85%, respectively. Antibody-mediated rejection occurred in 46% and was apparently reversed in 83% by plasma exchange and increased immunosuppression. The initial plasma exchange reduced immediate spin and AHG hemagglutination reactivity scores by 53.5 and 34.6%, respectively. Over the course of the pretransplant plasma exchanges, the immediate spin and AHG hemagglutination reactivity scores decreased by 96.4 and 68.5%, respectively. At 3 and 12 months, the immediate spin and AHG hemagglutinin reactivity scores and titers were less than those at baseline but greater than or equal to those on the day of transplantation. Despite an increase in scores and titers, antibody-mediated rejection was not present. Pre-transplant plasma exchange conditioning combined with other immunosuppressives can be used to prepare patients for ABO-incompatible kidney transplantation from living donors, but antibody-mediated rejection post-transplant is a common occurrence and allograft survival may be reduced. Controlled clinical trials are needed to identify the optimum conditioning for ABO-incompatible renal transplants.

The role of B cells and alloantibody in the host response to human organ allografts

Some human organ transplants deteriorate slowly over a period of years, often developing characteristic syndromes: transplant glomerulopathy (TG) in kidneys, bronchiolitis obliterans in lungs, and coronary artery disease in hearts. In the past, we attributed late graft deterioration to "chronic rejection", a distinct but mysterious immunologic process different from conventional rejection. However, it is likely that much of chronic rejection is explained by conventional T-cell-mediated rejection (TMR), antibody-mediated rejection (AMR), and other insults. Recently, criteria have emerged to now permit us to diagnose AMR in kidney transplants, particularly C4d deposition in peritubular capillaries and circulating antibody against donor human leukocyte antigens (HLA). Some cases with AMR develop TG, although the relationship of TG to AMR is complex. Thus, a specific diagnosis of AMR in kidney can now be made, based on graft damage, C4d deposition, and donor-specific alloantibodies. Criteria for AMR in other organs must be defined. Not all late rejections are AMR; some deteriorating organs probably have smoldering TMR. The diagnosis of late ongoing AMR raises the possibility of treatment to suppress the alloantibody, but efficacy of the available treatments requires further study.