William M. Lefor

Antiphospholipid antibodies are a risk factor for early renal allograft failure.

BACKGROUND Biopsy specimens of transplanted kidneys that fail to function reveal cellular infiltrates, infarcts, and thrombi. Because antibodies to phospholipids (aPA) and/or phospholipid-binding proteins have been associated with thrombosis, we asked whether aPA are a risk factor for early allograft failure. METHODS Final crossmatch sera from 56 patients with primary nonfunctioning renal allografts were tested for aPA. Serum from the next consecutive patient to undergo transplantation served as transplantation controls. Both groups were compared with aPA values obtained from testing 252 control individuals. The ELISA was designed to detect IgG, IgM, and IgA antibodies to phosphatidylserine, cardiolipin, and phosphatidylethanolamine. RESULTS Patients were evaluated based upon the aPA ELISA findings. aPA were present in 57% of the patients with early nonfunction renal allografts and 35% of the patients with functioning grafts (P=0.0234). aPA in previously hemodialyzed patients did not predict allograft failure or success (P=0.3766). In contrast, all nonhemodialysis patients who had aPA at the time of transplantation experienced early allograft failure (P=0.0022). CONCLUSIONS These data show that aPA are an important risk factor for early renal allograft failure. Furthermore, aPA-positive patients who have no history of hemodialysis are at the greatest risk. Pretransplantation aPA screening of renal transplant candidates forewarns of early graft failure and indicates which patients may benefit from anticoagulant therapy.

Hyperacute and acute kidney graft rejection due to antibodies against B cells

Because of the perception of its uncertain clinical significance, the B cell crossmatch is not universally performed before renal transplantation. Even though sporadic cases of hyperacute rejection associated with B cell antibodies have been reported, doubts remain in light of other studies suggesting no effect on graft survival. This report describes 4 cases of graft rejection (3 hyperacute and 1 acute) that occurred in patients with anti-B-cell antibodies specific against donor HLA-DR or DQ antigens. Absence of anti-donor class I antibodies was confirmed in all cases by 2-color flow cytometry. Strong evidence for an antibody-mediated mechanism was found in one patient with anti-class I and anti-class II antibodies in serum transplanted with a class II mismatched kidney. In this case, only anti-class II antibodies were recovered in the eluate of the nephrectomy specimen. These four cases were compiled from three different institutions over a four-year period, which confirms the infrequent occurrence of these events. While anti-class II antibodies may not always be detrimental for graft survival, these results also confirm that they have the potential to cause hyperacute or acute graft loss. We conclude that the information provided by the B cell crossmatch should be available at the time that a decision to proceed with a renal transplant is made.

Benefits of HLA-A and HLA-B Matching on Graft and Patient Outcome after Cadaveric-Donor Renal Transplantation

Data collected prospectively on 3811 renal transplantations performed between June 1977 and July 1982 by the 42 member institutions of the South-Eastern Organ Procurement Foundation were analyzed to determine the influence of donor-recipient HLA-A and HLA-B matching on patient and graft outcome. Well-matched recipients were more likely to have received kidneys from outside their own centers, were more highly presensitized, included fewer blacks, and were more likely to have lost an earlier graft. Multivariate Cox regression analysis that included these and six other potential confounding variables revealed a significant association (P less than 0.001) between good HLA-A and B matching and increased graft survival. The difference in mean (+/- S.E.) actuarial graft survival between recipients worst matched and best matched for HLA-A and B antigens increased with time: 55 +/- 2 per cent as compared with 64 +/- 4 per cent at six months and 18 +/- 4 per cent as compared with 44 +/- 7 per cent at four years. Poor HLA matching of donor with recipient provided the greatest relative risk (2.16) of irreversible graft rejection of all the variables examined. Among patients with functioning grafts, well-matched recipients had lower serum creatinine levels and received significantly smaller amounts of glucocorticoids. Our findings indicate that good HLA-A and B matching is highly dependent on a system for sharing organs among institutions, and results in decreased graft rejection, better long-term graft function, and less need for post-transplantation immunosuppression.

Multivariate analysis of risk factors in cadaver donor kidney transplantation

Data collected prospectively on 3811 kidney transplants performed between June 1977 and July 1982 with follow-up to July 1984 by the 42 member institutions of the South-Eastern Organ Procurement foundation were analyzed to identify factors associated with graft and patient outcome in patients not receiving cyclosporine. Multivariate Cox regression analysis was used to examine the association and relative risk of 24 variables with three actuarial outcomes: overall graft failure, irreversible rejection, and patient death. Factors having no suggested association with any outcome included: recipient sex, history of pregnancy, blood group, and time on dialysis; organ preservation method, time and source; donor race; crossmatch test sensitivity; and annual center transplant rate. In decreasing order of relative risk, the factors most significantly associated with irreversible rejection were: loss of two or more prior grafts, low HLA-A,B match, lack of pretransplant blood transfusion, high (greater than 60%) pretransplant sensitization to leukocyte (HLA) antigens, and delayed graft function. Splenectomy, insulin-dependent diabetes, and antilymphocyte serum therapy provided the greatest risk of patient death. Factors such as recipient age, race, and native nephrectomy had suggested associations with outcome. By adding each center as a separate covariate in the analysis, other center-dependent factors were quantitated and found in some cases to have a highly significant association with graft and patient outcome. These results provide a basis for evaluating the potential risk of graft loss or patient death for those prospective cadaver kidney transplant recipients not being considered for cyclosporine therapy.

The effect of HLA–A, –B matching on cadaver renal allograft rejection comparing public and private specificities

Data collected prospectively on 3811 cadaver renal transplants performed between June 1977 and July 1982 by the 42 member institutions of the South-Eastern Organ Procurement Foundation (SEOPF) were analyzed to determine whether donor-recipient compatibility based on public rather than private HLA-A,-B specificities influenced the beneficial effect of HLA matching on outcome. HLA compatibility was calculated considering match and mismatch based on common private or various public (crossreactive group, [CREG]) specificities. Donor-recipient compatibility using certain CREG assignments provided an equivalent means of stratifying graft outcome by the degree of HLA-A,-B match or mismatch, and other CREGs assignments did not. Multivariate Cox regression analysis of donor-recipient compatibility based on certain public antigens showed as high an association (P < 10−5) between good matching and decreased graft rejection as did matching for private antigens alone. Patient stratification by HLA match provided a stronger association with graft outcome than by HLA mismatch, irrespective of whether private or public antigens were considered. The likelihood of finding a better match was significantly increased using CREG assignments, and patients with at least one matched private antigen had equivalent or better graft survival when additional public antigens were matched. These findings indicate that with conventional immunosuppressive therapy: (1) matching of private or public HLA-A,-B antigens plays a highly significant role in decreasing renal allograft rejection; (2) matching based on certain public antigens can provide the same or a better association with outcome as private antigens; and (3) the association (crossreactivity) of various HLA specificities can be defined on a functional basis in terms of graft survival.

Lack of influence of donor-recipient differences in subtypic HLA-A,B antigens (splits) on the outcome of cadaver renal transplantation.

Data collected prospectively on 3811 cadaver renal transplants performed between June 1977 and July 1982 by the 42 member institutions of the South-Eastern Organ Procurement Foundation (SEOPF) were analyzed to determine whether donor-recipient differences in sub-typic HLA-A,B specialties (splits) influenced outcome. The number of HLA-A,B antigens matched and mismatched between each donor and recipient was calculated in three ways: (1) considering all antigens and splits as distinct (not matched); (2) considering all splits as only matched with their corresponding typic antigen (but not with each other); and (3) considering all splits as matched with both their corresponding typic antigen as well as each other. Overall graft survival, graft loss from irreversible rejection, and patient survival stratified by the level of HLA match were the same using all three methods. In addition, using multivariate Cox regression analysis, the strong association between good HLA matching and increased graft survival was the same using all three methods of matching. Patients with a given number of mismatched antigens had no significant decrease in survival when additional splits were considered mismatched with each other or their corresponding typic antigen. These results suggest that matching of typic HLA-A,B antigens plays a highly significant role in reducing graft rejection but that donor-recipient differences in splits have a negligible effect on graft outcome.

ANTIBODIES TO CROSSREACTIVE HLA ANTIGENS: EVALUATION BY CYTOTOXICITY, FLOW CYTOMETRY, AND INHIBITION OF MONOCLONAL ANTIBODY BINDING

Broadly sensitized patients have antibodies that react with cells from most individuals except those having HLA antigens similar to their own. In this work we addressed the question of whether crossreactive antigens could also be considered compatible. Broadly reactive sera were tested in multiple experiments against lymphocytes selectively mismatched for only one HLA-A, B antigen. Antibodies, measured by cytotoxicity and flow cytometry, were detected in most cases, and their prevalence was the same, regardless of whether the mismatched HLA antigen was crossreactive with the patients. There were several patients bearing one of the A2, B5, or B7 crossreactive group antigens with antibodies against another antigen of the group. Anti-HLA-A2 reactivity was further evaluated by testing the inhibitory effect of broadly reactive sera on the binding of an anti-HLA-A2 monoclonal antibody. Anti-A2 reactivity measured in this assay was detected in A28-positive patients as frequently as in A28-negative patients. These results suggest that antigens of several crossreactive antigen groups are significantly immunogenic and elicit antibodies as often as noncrossreactive antigens. Further studies are necessary to evaluate other less-frequent antigen combinations.

Use of SEOPF regional crossmatch trays to share kidneys for sensitized patients. Local experience of three centers.

Regional organ procurement (ROP) crossmatch trays are used by members of the South-Eastern Organ Procurement Foundation (SEOPF) to facilitate sharing of cadaver kidneys for highly sensitized patients. ROP trays carry a single representative serum sample from over 900 patients with panel reactive antibody (PRA) levels of ≤60%. Trays are centrally prepared periodically and distributed to member laboratories where they are used for preliminary crossmatching against locally obtained donors. Crossmatching results are used in conjunction with the SEOPF computer match program for sharing of kidneys. Proficiency testing studies by the 40-member laboratories show a >90% concordance rate on results with these highly and broadly reactive sera. Data were available from 3 centers on 74 kidneys shared between SEOPF-member institutions on the basis of a remote, preliminary, negative ROP tray crossmatch. Of these, 44 (59%) crossmatched negative locally with the same and other sera, and were thus considered acceptable to be transplanted to the intended highly sensitized patients. Sixteen (22%) donors had a positive crossmatch locally, but with sera other than that present on the ROP tray used for screening. In 14 cases (19%) the same serum as on the ROP tray gave a positive crossmatch. The majority of ROP tray inconsistencies appeared to be due to use of more sensitive crossmatching techniques at the recipient center. Of the 27 patients transplanted at these 3 centers with kidneys received on the basis of ROP tray results, none experienced hyperacute or early irreversible rejection and actual graft survival at 6–48 months is 74%. These studies indicate that regional sharing of patient sera by the existing network of histocompatibility testing laboratories is an effective and reliable mechanism to identify crossmatch-negative donors for highly sensitized patients.

Reasons why kidneys removed for transplantation are not transplanted in the United States

The Organ Center established by the South-Eastern Organ Procurement Foundation collected information on 575 kidneys procured but not transplanted in the United States. The greatest proportion, 393, were not transplanted because a crossmatch-negative recipient was not found. Of these kidneys, 260 were transported to at least one additional center and 115 were offered to an additional center within 24 hr of removal. In 18 instances, attempts to share kidneys were made too late. The blood group representation of these kidneys was 62% A, 15% B, 12% AB, 11% O. The SEOPF system of crossmatches enabling the donor center to perform crossmatches on immunized recipients from 42 other transplant centers still resulted in the loss of 98 kidneys. However, this loss was half that predicted from the national experience. Rather than discarding them, 272 kidneys were transported overseas where 183 were transplanted. Technical problems related to the deceased, organ size, anatomic abnormalities, expended or nonviable material for tissue typing, and perfusion failure led to discarding 182 kidneys. Only 15 kidneys were reported injured irremediably at the time of removal, while 12 had bacterial contamination. The data emphasize our national problem and demand collaboration and new systems for kidney distribution in recipients of non-O blood groups.

Positive crossmatches against mandatorily shared kidneys.

&NA; From October 1987 through February 1990 approximately 8.5% (29/341) of all donor kidneys shipped under the UNOS Mandatory Sharing Policy were denied to 27 intended recipients due to a positive final crossmatch [XM(+)]. The intended recipients included 18.5% hispanics and 7.4% blacks compared to 2.4% and 1.6%, respectively, for XM(-) recipients (1–3). Further, more were highly sensitized with 81% having a current PRA >10% and 56% with a peak PRA >80% compared to 65% and 14%, respectively, for XM(-) recipients. More importantly, 19/27 (70%) of the recipient candidates may have had irrelevant positive XMs. The XM(+) patients were classified into five categories defined by: I) autoantibodies; II) transfusions in the 2 weeks prior to the availability of the donor; III) the XM technique; IV) highly sensitized regraft candidates with current and peak PRAs >85% and V) antibody to unreported MHC antigens. Of these, 70% may have been denied a transplant due to IgM autoantibodies or the use of XM techniques lacking extensive evaluation. The authors propose that all XM(+) mandatorily-shared kidneys be examined for IgM autoantibody and that kidneys not be denied to potential recipients due to IgM autoantibody. In addition, to minimize exclusions based on positive B-cell XMs, it is proposed that man-datorily-shared kidneys be shared on the basis of the DR subtypes, insofar as is currently practical.