ABO incompatible kidney transplantation on triple therapy compared with quadruple therapy

The persistent elimination of B cells responding to blood group A carbohydrates by synthetic group A carbohydrates and B-1 cell differentiation blockade: novel concept in preventing antibody-mediated rejection in ABO-incompatible transplantation

We demonstrated a novel strategy for specific and persistent inhibition of antibody (Ab) production against blood group A or B carbohydrate determinants necessary for successful ABO-incompatible transplantation. Similar to human blood group O or B individuals, mice have naturally occurring Abs against human blood group A carbohydrates in their sera. B cells with receptors for A carbohydrates in mice belonging to the CD5+CD11b+B-1a subset have phenotypic properties similar to those of human B cells. These cells could be temporarily eliminated by injecting synthetic A carbohydrates (GalNAcα1–3, Fucα1–2Gal) conjugated to bovine serum albumin (A-BSA) and anti-BSA Abs. In mice that received the injection of A-BSA/anti-BSA Abs, the serum levels of anti-A IgM were reduced, but immunization with human A erythrocytes resulted in increased serum levels of anti-A Abs. When combined with cyclosporin A (CsA) treatment, which blocks B-1a cell differentiation, and treatment with A-BSA/anti-BSA Abs, the serum levels of anti-A Abs were persistently undetectable in the mice even after the immunization. B cells with receptors for A carbohydrates were markedly reduced in these mice. These results are consistent with the hypotheses that treatment with A-BSA/anti-BSA Abs temporarily depletes B cells responding to A determinants, and CsA treatment prevents the replenishment of these cells.

Association of treatment with 15-deoxyspergualin and BK virus nephropathy in kidney allograft recipients

OBJECTIVE

BK virus nephropathy (BKVN) has been proposed as an important cause of allograft dysfunction and loss in kidney allograft recipient over the last decade. Intense immunosuppression and tubular injury have been shown to promote the replication of polyomavirus. 15-deoxyspergualin (DSG), an effective immunosuppressive agent, is used as a rescue drug for acute rejection in clinical renal transplantation in Japan. To determine whether DSG is a risk factor for BKVN and outline the relationship among BKVN, DSG, and other risk factors, we analyzed 88 patients who received living-related renal transplantation between January 1999 and April 2003.

METHODS

A total of 114 biopsy specimens from 88 living-related kidney transplantation recipients (performed between January 1999 to April 2003) were retrospectively analyzed. Patients received immunosuppression therapy based on calcineurin inhibitors and corticosteroid [tacrolimus (TAC) 33 and cyclosporin (CyA) 55]. Additionally, mycophenolate mofeteil (MMF) was used in 21 patients; DSG was used in seven patients; and anti-CD3 monoclonal antibody was used in 16 patients. We analyzed the degree of donor/recipient human leucocyte antigen (HLA) compatibility assessed by the number of HLA-A, -B, and -DR-mismatched antigens in 88 patients. The diagnosis of BKVN was made by the light microscopic examination and a positive immunohistochemical staining of anti-40 antibody in biopsy specimens. Patients were divided into two groups of group A (mild histological change) and group B (moderate or severe histological change) to determine the risk factors in different histological staging. The clinical course of two typical patients in different histological stage is described briefly to outline the risk factors of BKVN.

RESULTS

We identified seven cases of BKVN (8.0%) from 88 transplanted patients. Significantly higher incidence of combination regimen consisting of TAC and MMF in BKVN group was noticed compared with non-BKVN group (57.1% vs. 9.9%; p = 0.003). BKVN was associated with a significantly higher incidence of DSG administration compared with non-BKVN group (57.1% vs. 3.7%; p </= 0.001). No difference was found in HLA mismatch between BKVN and non-BKVN group. Additionally, a significantly higher incidence of acute rejection episode prior to BKVN diagnosis was found in group B compared with group A (100% vs. 0%; p = 0.002), and the same statistical difference was shown in the number of anti-rejection therapy between group B and group A (100% vs. 0%; p = 0.002). We recognized a significant difference between group B and group A in terms of the combine regimen therapy of TAC with MMF (p = 0.002) and no difference in graft loss rate (p = 0.092), even though it was 50% in group B and was 0% in group A.

CONCLUSIONS

In this study, our data indicated excessive intense immunosuppression with TAC-MMF is related to the development of BKVN. In addition, we found that anti-rejection therapy, especially with DSG, may accelerate the development of BKVN.

Reversibility from delayed hyperacute rejection in ABO-incompatible renal transplantation: histopathological findings of renal allograft biopsy

ABO-incompatible renal transplantation (ABOIRTx) tend to lead to blood type antibody-mediated rejection, the so-called delayed hyperacute rejection (DHAR), which results in short-term graft loss. To clarify the accurate incidence and prognostic value of DHAR among ABOIRTx, we reviewed biopsy specimens obtained from ABOKTx allografts with abrupt dysfunction during the early period after transplantation. Among 74 ABOIRTx patients, 34 patients displayed allograft dysfunction within 14 days following transplantation. The biopsy specimens were classified based on the Banff schema. The pathological diagnosis of ABO blood type antibody-mediated humoral rejection (ABO-AMHR) was made by the following 3 findings: Specimens with all of above-mentioned findings were categorized as severe ABO-AMHR; those with at least one findings, were categorized as mild ABO-AMHR. All patients were treated with steroid pulse therapy and/or modification of other immunosuppressants. Group 1 consisted of severe ABO-AMHR (n = 6); group 2 consisted of mild ABO-AMHR (n = 5); group 3 consisted of acute cellular rejection (n = 3); group 4 consisted of recovery phase of ATN (n = 11); group 5 consisted of calcineurin inhibitor toxicity (n = 2); and group 6 consisted of normal histology (n = 5). One of 6 patients (16%) in group 1 lost the graft because of DHAR irreversible by antirejection and anticoagulation therapy. However, there has been no clear definition of histpathological criteria for DHAR after ABO-incompatible kidney transplantation. The definition must prognosticate whether the rejection process is reversible.

NOD/SCID mice engrafted with human peripheral blood lymphocytes can be a model for investigating B cells responding to blood group A carbohydrate determinant

Human antibodies (Abs) against blood group A or B carbohydrate determinant are a major barrier to ABO-incompatible organ transplantation; however, the phenotype and other properties of B cell types responding to A or B carbohydrate epitopes have not been defined. Studies here, which use fluorescein-labeled synthetic A determinant (GalNAcalpha1-3Fucalpha1-2Gal), demonstrate that B cells bearing surface IgM (sIgM) receptors recognizing blood group A carbohydrate determinant are found exclusively in a small B cell subpopulation, i.e. sIgM+ CD11b+ CD5+ B1 cells, in blood group O human peripheral blood mononuclear cells (PBMC). In order to test anti-A Abs producing capacity of the human PBMC, nonobese diabetic (NOD)/severe combined immune-deficient (SCID) mice that have been treated with rabbit anti-asialo GM1 serum to deplete natural killer cells and with 3 Gy of whole body irradiation were engrafted with blood group O or A human PBMC, followed by sensitization of human blood group A red blood cells. Anti-A-specific human Abs were detected in the sera of the mice that received blood group O human PBMC, whereas they were not detected in the sera of the mice that received blood group A human PBMC, indicating profound tolerance of auto-reactive B cells. The human PBMC-NOD/SCID chimera developed by injection of blood group O human PBMC might be a useful in vivo model to test effects of immunosuppressants or other approaches on human B cells that respond to blood group A antigens.