Harriet Noreen

The role of natural antibodies in the activation of xenogenic endothelial cells.

Hyperacute rejection of organ xenografts is thought to be mediated by the reaction of naturally occurring antibodies and complement of the recipient with blood vessels in the donor organ. We have suggested previously that the pathogenesis of hyperacute rejection might involve the activation of endothelial cells in the graft. To evaluate the potential role of natural antibodies and complement in hyperacute xenograft rejection, sixteen human sera were tested for variation in the ability to activate porcine endothelial cells as manifested by the release of biosynthetically labeled heparan sulfate from the cells. It was then asked to which extent such variation might reflect differences in natural antibody titer and/or complement activity. The sera mediated release of 3.6–57% of endothelial cell-associated heparan sulfate. Heparan sulfate release correlated significantly with the titer, in the sera, of IgM antibodies that bound to cultured endothelial cells (P=0.0008) or to a triad of glycoproteins believed to represent the major targets of natural antibodies in porcine to primate xenografts (P=0.001); correlation was also observed with the total concentration of IgM (P=0.0046). The release of heparan sulfate did not correlate with corresponding properties of serum IgG, with anti-swine hem-agglutination or with isohemagglutination titers. Heparan sulfate release correlated with deposition on endothelial cells of iC3b (P=0.0095), but not with serum complement activity. Our findings indicate that in the reaction between human serum and xenogeneic endothelial cells, it is the concentration of xenoreactive IgM and not differences in complement activity that limits the ensuing pathophysiologic events.

HLA alloimmunization in patients requiring Ventricular assist device support

BACKGROUNDnVentricular assist devices (VADs) are often necessary to maintain circulation in patients with heart failure prior to cardiac transplantation. However, the use of such devices has been reported to be associated with a high incidence of development of human leukocyte antigen (HLA) antibodies, due perhaps, according to some investigators, to immune-activating properties of the VAD itself. We looked at HLA antibody formation in our patients during VAD support to determine the rate and potential causes of antibody formation.nnnMETHODSnBetween 1995 and 2000, 54 patients were placed on a VAD at our institution. We reviewed clinical and blood transfusion history and HLA antibody testing of the 29 patients without HLA antibodies prior to implantation. HLA antibody testing was performed by an anti-globulin-augmented cytotoxicity method or by a commercial enzyme-linked immunoassay (ELISA) kit.nnnRESULTSnEight of 29 patients (28%) developed HLA antibodies. Patients who developed HLA antibodies after VAD implantation received significantly more total peri- and post-operative transfusions than did those who remained negative (99 transfusions vs 34 transfusions, p = 0.0014). Within this small study group, gender, age, etiology of heart failure, previous cardiac surgery and duration of VAD support showed no statistically significant correlation with formation of HLA antibodies.nnnCONCLUSIONSnOur data suggest that HLA alloimmunization during VAD support may be due to extensive blood transfusion. The rate of HLA alloimmunization does not appear to be greater than that reported in other populations of multi-transfused patients. Leukoreduction of cellular components, as well as plasma, or other initiatives is needed to reduce the rate of alloimmunization and, potentially, the wait to transplantation.

DNA HLA-DR typing results of 4000 kidney transplants

Recipients (4076) and donors (3325) of kidney transplants performed at 110 transplant centers were typed for HLA-DRB by the DNA RFLP method. The discrepancy rate of replicate samples distributed among 8 participating laboratories was a low 2.6%. The discrepancy rate between RFLP-DRB and serological HLA-DR typings was 25.0% for organ donors and 27.6% for kidney recipients. Discrepancy rates at the different transplant centers ranged from 9.7% to 86.7%. The discrepancies consisted of antigens being incorrectly interpreted by serology (16.8%), and of serological blanks turning out to be definable alleles by the DNA method (10.8%). The alleles that were mainly affected by discrepancies were DR1, DR8, DR10, DR12, DR13, DR14, DR16, DR17.2, and DR18.

DR2+ haplotypes in insulin-dependent diabetes: Analysis of DNA restriction fragment length polymorphisms

Insulin-dependent diabetes (IDD) is strongly associated with certain HLA class II (Ia) antigens. The frequency of DR2 is significantly reduced in IDD; among DR2+ patients, the frequency of the subtype specificity Dw2 defined with homozygous typing cells (HTCs) is significantly reduced compared to DR2+ controls, and the specificity LD-MN2, which we have defined using primed lymphocyte typing reagents, is significantly increased. We have studied DNA restriction fragment length polymorphisms (RFLP) of DR2-LD-MN2+ individuals and homozygous typing cells carrying specificities antigenically related to LD-MN2. Using a number of different restriction enzymes, a characteristic pattern of fragments could be defined for DR2-LD-MN2 using both DQ beta and DR beta cDNA probes. This pattern was shared with some but not all of the antigenically related HTCs, and was distinct from that of DR2-Dw2. The RFLP pattern of DR2-LD-MN2 obtained with the DQ beta probe is identical, except for one band, to that of DR1-Dw1, suggesting that at least some part of the DQ region is identical in these two haplotypes. These results indicate that analysis of RFLP patterns can be used to help identify the genetic regions and, eventually, genes most important in the association of HLA and IDD.

KIR3DL1/HLA-B Subtypes Govern Acute Myelogenous Leukemia Relapse After Hematopoietic Cell Transplantation

Purpose Disease relapse remains a major challenge to successful outcomes in patients who undergo allogeneic hematopoietic cell transplantation (HCT). Donor natural killer (NK) cell alloreactivity in HCT can control leukemic relapse, but capturing alloreactivity in HLA-matched HCT has been elusive. HLA expression on leukemia cells-upregulated in the post-HCT environment-signals for NK cell inhibition via inhibitory killer immunoglobulin-like (KIR) receptors and interrupts their antitumor activity. We hypothesized that varied strengths of inhibition among subtypes of the ubiquitous KIR3DL1 and its cognate ligand, HLA-B, would titrate NK reactivity against acute myelogenous leukemia (AML). Patients and Methods By using an algorithm that was based on polymorphism-driven expression levels and specificities, we predicted and tested inhibitory and cytotoxic NK potential on the basis of KIR3DL1/HLA-B subtype combinations in vitro and evaluated their impact in 1,328 patients with AML who underwent HCT from 9/10 or 10/10 HLA-matched unrelated donors. Results Segregated by KIR3DL1 subtype, NK cells demonstrated reproducible patterns of strong, weak, or noninhibition by target cells with defined HLA-B subtypes, which translated into discrete cytotoxic hierarchies against AML. In patients, KIR3DL1 and HLA-B subtype combinations that were predictive of weak inhibition or noninhibition were associated with significantly lower relapse (hazard ratio [HR], 0.72; P = .004) and overall mortality (HR, 0.84; P = .030) compared with strong inhibition combinations. The greatest effects were evident in the high-risk group of patients with all KIR ligands (relapse: HR, 0.54; P < .001; and mortality: HR, 0.74; P < .008). Beneficial effects of weak and noninhibiting KIR3DL1 and HLA-B subtype combinations were separate from and additive to the benefit of donor activating KIR2DS1. Conclusion Consideration of KIR3DL1-mediated inhibition in donor selection for HLA-matched HCT may achieve superior graft versus leukemia effects, lower risk for relapse, and an increase in survival among patients with AML.

Renal transplantation between living-related sibling pairs matched for zero-HLA haplotypes.

The functional survival rates of kidney grafts from zero-HLA haplotype-matched sibling pairs are similar to one-haplotype-matched pairs and superior to cadaver grafts. From January 1980 to March 1988, 318 primary renal transplants from sibling donors (151 matched for two, 130 for one, and 37 for zero HLA haplotypes), and 352 cadaver graft transplants were performed at the University of Minnesota. The renal graft survival rates at two years were 94%, 91%, and 94% for the 2, 1, and 0-haplotype pairs versus 75% for cadaver graft recipients (P less than 0.04). When analyzed across the different immunosuppression protocols the same trends held up, similar graft functional survivals for 1- and 0-haplotype-matched pairs both being superior to cadaver graft recipients. The graft functional survival rates at two years of recipients of 0-haplotype-matched sibling donor grafts (n = 37) was 94% versus 80% for recipients of cadaver donor grafts matched for greater than or equal to 4 HLA antigens. In addition, for recipients of 0-haplotype-matched grafts, hospital stay was shorter, fewer patients required dialysis posttransplant, and, despite a slightly higher incidence of rejection episodes (51% versus 40%, P = ns), the creatinine values one year posttransplant were significantly lower (1.5 mg/dl versus 1.9 mg/dl, P less than 0.02) than those of recipients of cadaver grafts matched for greater than or equal to 4 HLA antigens. These data support the use of cadaver grafts for patients not having a willing sibling donor, and the use of all willing sibling donors, whether or not they are a zero-haplotype match, for patients fortunate to have that family commitment.

The effect of mismatching for HLA-DR in recipients of renal allografts sharing one HLA-ABC haplotype with related donors

The effects of mismatching for DR antigens on renal allograft survival rates have largely been restricted to analyses of cadaver transplant results. Analyses of HLA matching in recipients of transplants from related donors have focused on the number of haplotypes shared between the recipients without regard to DR, or on the total number of HLA antigens mismatched, or on the degree of MLC responsiveness of the recipient to the donor. Most related donor-recipient pairs sharing only one HLA haplotype will be mismatched for DR at the other haplotype, but because there are a limited number of DR alleles, sharing of DR antigens on the mismatched haplotypes occurs relatively frequently. To determine the influence of mismatching for DR on the fate of renal allografts from related donors, we analyzed the results of 172 kidney transplants from related donors who shared one HLA-ABC haplotype with the recipient. There were 156 primary grafts and 16 retransplants; 147 donor-recipient pairs were satisfactory typed for DR antigens. Because genotyping was not usually done, we performed two analyses under two different assumptions. The first assumption was that individuals expressing less than or equal to 1 DR antigen had null antigens, or were homozygous for DR; the alternative assumption was that blanks were true antigens and individuals with blanks were heterozygous. The first assumption is more likely to be correct, and is the assumption used in most analyses of the effect of DR antigen mismatches on the results of cadaveric transplantation. Under the first assumption, of the 147 related donor-recipient pairs in whom DR typing was satisfactory, 33% were mismatched for 0, 64% for 1, and 3% for 2 DR antigens. The one-year absolute graft survival rates in recipients of kidneys from donors with 0 mismatches for DR was 92% (n = 49); in those with one mismatch for DR it was 82% (n = 94); and from those with two mismatches it was 50% (n = 4). The one-year graft survival rate in 25 donor-recipient pairs in which one or both members could not be satisfactorily DR typed was 76%. Differences in graft survival rates between the 0 and 1 and the 1 and 2 DR-mismatched groups were not statistically significant.(ABSTRACT TRUNCATED AT 400 WORDS)

Renal allograft survival in patients with positive B cell crossmatch to their donor.

B cell crossmatches were performed at cold (4 C) and warm (22 C and 37 C) temperatures on 193 renal allograft recipients with negative T cell crossmatches to their donor; 152 of the patients were also tested for autoantibody to autologous B cells. Fifty-six (29%) had a positive B cell crossmatch (21 cold, 35 warm); 14 were autoantibody positive, 23 autoantibody negative, and 19 were not tested for autoantibody. There were no differences in HLA-A, B, C, or DR antigen disparity between the B cell positive (14, 0 DR mismatch; 25,1 DR mismatch; 9, 0 DR mismatch) and the B cell negative group (40, 0 DR mismatch; 57,1 DR mismatch; 13, 2 DR mismatch). Similarly, age, diabetic status, and number and type of pretransplant blood transfusions were comparable between B cell positive and negative groups. Although there were no hyperacute rejections, 2-year actuarial graft survival was significantly lower in the B cell positive group, regardless of donor source, graft number, or temperature of reaction. Patients with a positive B cell crossmatch, presumably due to demonstrable autoantibody, may have better graft survival rates than patients with a positive B cell crossmatch and no autoantibody.

Survival of DNA HLA-DR typed and matched eadaver kidney transplants

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DNA typing: an important step forward?

In a collaborative project which was supported by 96 transplant centers, DNA typing of HLA-DR antigens was carried out on over 7,000 transplant donors and recipients at 8 participating laboratories. Approximately 25% of the individuals were found to have been typed incorrectly by serological means. An analysis of over 2,500 first cadaver kidney transplants showed a significant correlation of matching for the HLA-DR antigens in transplants where the serological typing was confirmed by DNA typing. In transplants where the serological typing was found to be incorrect, the analysis of serological HLA-DR mismatches resulted in no correlation with graft outcome whereas a significant correlation was found when the corrected DNA typed HLA-DR antigens were analyzed. Transplants which had been reported to the Collaborative Transplant Study based on serological typing as matched for HLA-A, -B, -DR or HLA-B, -DR were found to have a superior graft survival rate only if HLA-DR compatibility was confirmed by DNA typing.