BACKGROUND:

: Desensitization protocols have been developed to allow successful kidney transplantation in sensitized recipients. However, a detailed analysis of the impact of these protocols on alloantibody has not been performed.

METHODS:

: We studied 12 living-donor kidney-transplant recipients with positive antihuman globulin-enhanced complement dependent cytotoxicity (AHG-CDC) crossmatches against their donors. Using a variety of crossmatch techniques and single-antigen flowbeads (SAFBs), we characterized the specificity and amount of alloantibody at baseline before desensitization, after desensitization (using plasmapheresis followed by 100 mg/kg intravenous immunoglobulin, and anti-CD20 antibody), and 4 months after transplantation (after splenectomy and on maintenance immunosuppression).

RESULTS:

: All 12 patients with a positive baseline AHG-CDC crossmatch were AHG-CDC crossmatch negative at the time of transplant (after desensitization). However, despite desensitization, the majority of patients had low-level donor-specific alloantibodies demonstrable on the day of transplantation by both flow crossmatch (FXM 8/12) and SAFBs (10/11). Four months after transplantation, no patient had a positive AHG-CDC crossmatch, but again the majority had persistent low levels of donor-specific alloantibodies by FXM (6/12) and SAFBs (9/11). No patient experienced hyperacute rejection, and the persistence of low levels of donor-specific alloantibodies did not correlate with the development of humoral rejection in the early posttransplant period.

CONCLUSIONS:

: Despite desensitization, a majority of positive crossmatch transplant recipients demonstrate low levels of donor-specific alloantibodies both on the day of transplant and 4 months after transplantation. The impact of these antibodies appears to be minimal early after transplant, but their long-term significance bears further study.

BACKGROUND:

Preformed HLA antibodies (Ab), reported as panel-reactive antibody (PRA), prolong patient waiting time for kidney transplantation. We hypothesized that rituximab (RTX) could reduce PRA via B-cell depletion. This initial study reports the safety, pharmacokinetics, and pharmacodynamics of RTX in patients with end-stage renal failure.

METHODS:

The study was an investigator-initiated single-dose, dose-escalation phase I trial of RTX in chronic dialysis patients (PRA >50%). It was approved by the Institutional Review Board and the Food and Drug Administration. Nine subjects were treated with a single dose of RTX (n=3 per group) at 50, 150, or 375 mg/m. Peripheral lymphocyte cell surface markers and HLA Ab levels (%PRA and titers) were tested using flow cytometry.

RESULTS:

There were four significant adverse events: a suspected histoplasmosis infection; two Tenchkoff dialysis catheter infections; and fever (38.7 degrees C) during infusion. At 2 days after RTX therapy, there was depletion of CD19 cells (pre-RTX 181+/-137 vs. post-RTX 12+/-5.6, P =0.006). In 2 (22%) of 9 subjects, there was no appreciable change in PRA. Among the other seven patients, one had a decrease in PRA from 87% to 51% with a concurrent decrease in fluorescence intensity; five patients had changes in histogram architecture suggesting loss of antibody specificity; and one patient had a fourfold decrease in PRA titer from 1:64 to 1:16 at 6 months after treatment. In addition, one of the seven patients converted a donor-specific crossmatch to negative and underwent a successful living donor kidney transplantation.

CONCLUSIONS:

RTX can be safely administered and may be an effective agent to reduce high-titer anti-HLA Abs in subjects awaiting kidney transplantation.

Sensitization can present a virtually insurmountable barrier to kidney transplantation. Ten to twenty percent of patients on waiting lists for renal transplantation have developed broadly reactive cytotoxic antibodies against HLA antigens caused by pregnancy, blood transfusion, or a prior failed allograft. These sensitized end-stage renal disease patients often wait more than 5 years for a kidney to be offered. Potent immunosuppressives, plasma exchange and/or immunoadsorption have been used but the risk of infection limited their use. Some reports, have demonstrated in small numbers of patients the use of Intravenous Immunoglobulin (IVIG) as potential modality for the treatment of these sensitized patients. The goal of this study was to investigate the extent of the efficacy and to assess the utility of this modality of treatment on a relatively larger number of patients. The study included 11 patients with end stage renal disease who were waiting for living related renal allotransplantation. All patients had persistently positive crossmatches with their living related donors and PRA titer >/=20%. They received IVIG for a period of two weeks and a total of 6 doses. None of these patients, however, attained significant suppression of anti-HLA antibodies titer or a negative crossmatch reaction. We found that IVIG alone couldn't effectively inhibit preformed anti-HLA antibodies to allow successful renal transplantation.

BACKGROUND:

Sensitization to human leukocyte antigens (HLA) is a significant barrier to transplantation. Currently, no proven therapy exists to improve access to transplantation for highly sensitized patients. Here, we report a novel approach using intravenous immune globulin to modulate anti-HLA antibody and improve the chances for successful transplantation.

PATIENTS AND METHODS:

Forty-five highly HLA-sensitized patients presented as candidates for living-donor kidney transplantation (n=28), cadaveric kidney transplantation (n=15), or heart transplantation (n=2). All patients had a positive CDC crossmatch (CMX) with their donors. In living-donor recipients, intravenous immune globulin (IVIG) was added to the CMX evaluation to determine whether blocking antibodies present in IVIG could inhibit cytotoxicity. For those who showed in vitro inhibition with IVIG (n=26), IVIG was administered (usually as a single dose, 2 g/kg) and the CDC CMX was repeated against the prospective donor immediately after IVIG infusion. If negative, the patient underwent transplantation with their living-donor kidney within 24 to 72 hr. A similar but modified protocol was performed for cadaver donor candidates, all of whom were highly sensitized and had had CMX positivity with multiple donors, negating transplantation. Reductions in CMX positivity, posttransplantation serum creatinine level, number and severity of rejection episodes, and patient and graft survival rates were determined.

RESULTS:

Forty-two patients underwent transplantation. IVIG treatment completely abrogated the donor-specific CMXs in 35 of 42 patients. In the remaining 7 patients, the CDC CMX was inhibited, but flow cytometry CMXs remained positive. A total of 13 (31%) of 42 recipients developed rejection episodes 3 to 49 days after transplantation. Three grafts (7%) were lost to rejection. Mean serum creatinine level at 24 months was 1.4+/-0.4 mg/dL. Patient and graft survival rates were 97.6% and 89.1%, respectively, at 24 months.

CONCLUSIONS:

The in vitro IVIG CMX technique predicts the ability of IVIG to reduce anti-HLA antibody levels in highly sensitized patients. Subsequent in vivo IVIG treatment of responders eliminates the positive CDC CMX and allows for successful transplantation. Thus a positive CMX result is not necessarily a contraindication for transplantation and allows access to transplantation for patients for whom it was previously contraindicated.

Many patients who have an otherwise acceptable living-kidney donor do not undergo transplantation because of the presence of antibodies against the donor cells resulting in a positive crossmatch. In the current study, 14 patients with a positive cytotoxic crossmatch (titer </= 1 : 16) against their living donor underwent a regimen including pretransplant plasmapheresis, intravenous immunoglobulin, rituximab and splenectomy. Eleven of 14 grafts (79%) are functioning well 30-600 days after transplantation. Two grafts were lost to accelerated vasculopathy and one was lost to death with good function. No hyperacute or cellular rejections occurred. Antibody-mediated rejection occurred in six patients [two clinical (14%) and four subclinical (29%)] and was reversible with plasmapheresis and steroids. Our results suggest that selected crossmatch-positive patients can be transplanted successfully with living-donor kidney allografts, using a protocol of pretransplant plasmapheresis, intravenous immunoglobulin, rituximab and splenectomy. Longer follow-up will be needed, but the absence of anti-donor antibody and good early outcomes are encouraging.

BACKGROUND:

A positive crossmatch with a "current" recipient serum (drawn shortly before the proposed transplant) is a contraindication to renal transplantation because of the risk of hyperacute rejection. Conflicting data have been reported concerning the significance of a positive crossmatch with "remote" sera (obtained months or years earlier) when the current crossmatch is negative.

METHODS:

Recipients of a first or second cadaver transplant between June 1988 and April 1994 were studied. All transplants were performed with a negative "current" crossmatch. Retrospective crossmatches using "remote" sera were performed for all sensitized recipients.

RESULTS:

Recipients with a positive remote crossmatch (RXM) demonstrated a higher incidence of delayed graft function and of acute rejection and graft loss occurring in the first year posttransplant than did sensitized recipients with a negative RXM or unsensitized recipients. In multivariate analysis, only recipients with both a positive RXM and delayed graft function were at significantly higher risk for graft loss. Grafts surviving the first year demonstrated similar half-lives whether the RXM was positive or negative.

CONCLUSIONS:

The positive RXM, possibly in conjunction with other factors leading to very early graft damage, is a significant predictor of unfavorable transplant outcome in first and second renal transplants. This effect is seen early in the transplant course, and there seems to be no impact on outcome after the first year. Newer immunosuppressive modalities may help to reduce the early negative impact.

BACKGROUND:

Preexisting alloantibodies against the mismatched HLA class I antigens of the donor, when present in current sera, are believed to be detrimental for kidney graft survival. The relevance of a positive crossmatch with historical sera only is still a matter of debate. Previous studies showed a correlation between the presence of alloantibodies and the presence of alloactivated cytotoxic T lymphocytes (CTLs). We wondered whether the persistence of activated CTLs might explain the poor results in a proportion of patients with a historical positive crossmatch.

METHODS:

We tested 10 sensitized patients to determine whether activated CTLs persist when the antibodies disappear. Limiting dilution assays were performed in the presence and absence of cyclosporine (CsA) to distinguish between activated (primed) (CsA resistant) and naive (CsA sensitive) CTLs. To test the clinical relevance of the persisting CTLs, eight sensitized patients, who underwent a kidney transplantation across a positive historical crossmatch, were retrospectively tested for the presence or absence of activated donor-specific CTLs at the day of transplantation.

RESULTS:

In the first group, four patients had CsA-sensitive CTLs, three patients had CsA-resistant CTLs, and three other patients had CsA-sensitive CTLs for a particular HLA antigen and CsA-resistant CTLs for another HLA antigen. In the transplant group, four patients with CsA-sensitive CTLs at the day of transplantation were found to have a good graft function. In the other four patients, the presence of CsA-resistant donor-specific CTLs was associated with rejection and early graft loss.

CONCLUSION:

The present study suggests that determining the activation state of CTLs specific for the HLA mismatch against which antibodies were present in historical sera, may be relevant to transplant outcome in patients who undergo transplantation across a positive historical crossmatch.

Transplantation of patients possessing antibodies against allo-HLA antigens can be delayed for years. We have shown that administration of intravenous immunoglobulins (IVIg) can induce a profound and sustained decrease in the titers of anti-HLA antibodies. We report here the first series of patients desensitized, then transplanted using IVIg therapy. Fifteen patients have been included and treated with IVIg, given as 3 monthly courses of 2g/kg body weight. Thirteen of those 15 patients (87%) were effectively desensitized and underwent immediate transplantation. Eleven were transplanted with a cadaveric donor, and two with a living donor against which the pretreatment cross-match was positive. One graft was lost from thrombosis and one from rejection. All other patients had uneventful courses, without any episodes of rejection, with a follow-up of more than 1 year. Thus, IVIg therapy allows safe and prompt kidney transplantation of immunized patients.