Human Leukocyte Antigen Antibody Levels Research Articles

I Got It from My Mamma: Sensitization by Transplacental Transfer of Maternal HLA Antibodies Managed with Manual Exchange Transfusion

<h3>Introduction</h3> During pregnancy antibodies are passed from mother to fetus with many known immunologic benefits. There is no data about the implications of this on pediatric transplant immunology. We report a case of transplacental transfer of maternal Human Leukocyte Antigen (HLA) antibodies affecting cardiac transplant candidacy in an infant with cardiomyopathy. <h3>Case Report</h3> A 3-week-old Amish boy with a homozygous MYBPC3 mutation causing severe cardiomyopathy admitted for refractory heart failure symptoms was referred for heart transplant evaluation. Labs were notable for high levels of high Mean Fluorescence Intensity (MFI) HLA antibodies (Panel of Reactive Antibodies (PRA) Class I: 74%, Class II: 80%) with no known sensitizing events. Maternal history was remarkable for multiple miscarriages raising the question that his HLA antibodies could be a result of maternal HLA sensitization with transplacental antibody transfer versus active antibody production by the child. Subsequent antibody testing of his mother's blood and breast milk revealed nearly identical HLA antibody profiles to that of the patient. Given the patient's prohibitively small size for antibody removal by plasmapheresis, we elected to perform double volume whole blood exchange transfusions with serial monitoring of his HLA antibodies. Considering his severe ventricular dysfunction, exchange transfusions were performed manually via the push pull method over 6 hours. He ultimately underwent 6 exchange transfusions over the course of 7 weeks. Serial antibody testing revealed a progressive decline in all his HLA antibody levels to <3,000 MFI with only mild rebound after each transfusion consistent with tissue redistribution rather than active antibody production. He was successfully transplanted with a negative PRA (Class I: 0%, Class II: 0%) without post-transplant complications. <h3>Summary</h3> We believe this is the first report demonstrating transplacental acquisition of maternal HLA antibodies in an infant successfully removed via serial whole blood exchange transfusions enabling successful cardiac transplantation.

Ultraviolet light-based pathogen inactivation and alloimmunization after platelet transfusion: results from a randomized trial.

The current study explored whether pathogen-reduction treatment of platelet components before transfusion would decrease the risk of alloimmunization. Study participants were patients with hematologic cancer who were included in two parallel, randomized clinical trials testing pathogen-reduction treatment versus conventional platelets using the Mirasol or Intercept pathogen-reduction systems. Patients who had a baseline, pretransfusion sample and a follow-up, posttransfusion sample were included in the study (n = 179 patients in each study arm). Human leukocyte antigen antibody levels were determined using a commercial multianalyte, bead-based assay. The rate of human leukocyte antigen Class I alloimmunization at the clinical sites in recipients of conventional platelets was low at the highest assay cutoff (range, 1.2%-5.9%). Consistent with prior studies, human leukocyte antigen antibodies were first detected from 3 to 35 days after transfusion. There were no statistically significant differences between alloimmunization rates in patients who received pathogen-reduction treatment versus conventional platelet transfusions. Although he difference was not statistically significant, the effect size for protection from alloimmunization was greatest for high-level human leukocyte antigen Class I antibodies (approximately threefold) in the Intercept-treated patients compared with those who received conventional platelets. In the Mirasol study, only two patients and one patient in the control group developed medium-level or high-level antibodies, respectively, so it was impossible to determine an effect size for potential protection. The current study was not sufficiently powered to determine whether pathogen-reduction treatment provides protection from human leukocyte antigen alloimmunization in platelet transfusion recipients. The data presented will be useful in the design of future trials and endpoints powered to detect a protective effect.

Human Leukocyte Antigen Sensitization in Solid Organ Transplantation: A Primer on Terminology, Testing, and Clinical Significance for the Apheresis Practitioner.

The human leukocyte antigen (HLA) system is an important immunologic barrier that must be considered for successful solid organ transplantation. Formation of donor-specific HLA antibodies in solid organ transplantation is an important cause of allograft injury and may contribute to recipient morbidity and mortality. Therapeutic plasma exchange is often requested to lower HLA antibody levels prior to or after transplantation and for management of HLA antibodies in the context of organ rejection. In this review, we summarize the current terminology, laboratory testing, and clinical significance of HLA sensitization in the solid organ transplant population. Furthermore, to illustrate applications of HLA testing in clinical practice, we summarize our own lung and kidney institutional protocols for managing HLA antibodies in the peri-transplant setting.

Nephrectomy for the failed renal allograft in children: predictors and outcomes

There are no guidelines for the removal of a failed renal allograft, and its impact on subsequent dialysis and retransplantation has not yet been described. We performed a 10-year review of allograft failure to study the factors that determined an outcome of transplant nephrectomy and choice of subsequent renal replacement therapy in children with or without nephrectomy. A total of 34 children developed graft failure over the 10-year study period, of whom 18 (53 %) required transplant nephrectomy. The median graft survival was 1.1 (range 0.2-10.6) versus 7.5 (1.5-15.0) years in the nephrectomy and non-nephrectomy groups, respectively (p = 0.011). Children with graft failure within 1 year of transplantation were four-fold more likely to require transplant nephrectomy than those with graft failure after 1 year (p = 0.04). Renal biopsy performed at ≤ 8 weeks prior to graft loss showed Banff grade II acute rejection in 13 of the 18 children who required subsequent nephrectomy versus three of the 13 children who did not need nephrectomy (p = 0.01). Inflammation (fever, graft tenderness and raised C-reactive protein (CRP) in the 2 weeks preceding graft failure) was seen in 66 % of nephrectomized children, but not in any in the non-nephrectomy group (p = 0.0003 for CRP between groups). Banff II rejection, an inflammatory response and the time post-transplantation significantly and independently predicted the outcome of nephrectomy (p = 0.008, R (2) = 67 %). Human leukocyte antigen (HLA) antibody levels after graft failure were higher in the nephrectomy group (p = 0.0003), but there was no difference between groups in terms of the presence or class of donor-specific antibodies. Of the children with graft failure, 82 % required dialysis (61 % hemodialysis) and 35 % have to date been successfully retransplanted. Children with Banff II rejection, an inflammatory response and early graft loss are more likely to require transplant nephrectomy. Nephrectomy may be associated with higher circulating HLA antibody levels.

Proteasome inhibition by bortezomib: Effect on HLA-antibody levels and specificity in sensitized patients awaiting renal allograft transplantation

BackgroundSensitization to human leukocyte antigen (HLA) prolongs waiting list time and reduces allograft survival in solid organ transplantation. Current strategies for pretransplant desensitization are based on B-cell depletion and extracorporeal treatment. The proteasome inhibitor bortezomib allows direct targeting of the antibody-producing plasma cell and has been used in antibody-mediated rejection (AMR) and recipient desensitization with varying results. Here, we report the effect of bortezomib preconditioning on HLA antibody titers and specificity in highly sensitized patients awaiting renal allograft transplantation. Patients and methodsTwo highly sensitized patients awaiting third kidney transplantation were given one cycle of bortezomib (1.3mg/m², days 1, 4, 8, 11), as part of recipient desensitization. Time-course and levels of anti-HLA antibodies, as well as specificity to previous transplant antigens were monitored by luminex technology. In addition, measles and tetanus toxoid immunoglobulin G (IgG) was measured. ResultsFollowing bortezomib, overall changes in IgG levels were small and no sustained reduction in anti-HLA class I or II antibody levels was observed over more than 100days of follow-up to both, donor specific and non-donor specific antigens. Moreover, anti-measles and -tetanus toxoid IgG levels remained unchanged. ConclusionsBortezomib preconditioning alone does not result in sustained reduction of HLA antibody levels or alter protective immunity in sensitized patients. This supports the notion, that bortezomib requires activation of plasma cells, as in AMR, to effectively reduce HLA antibody production. Hence, in a pretransplant setting, combination strategies may be required to derive benefit from proteasome inhibition.

How Does Auxiliary Liver Transplantation Regulate Alloreactivity in Sensitized Kidney Transplant Patients?

Many potential recipients with high-preformed human leukocyte antigen antibody levels wait significantly longer than unsensitized patients for a compatible donor kidney or are even worse; patients remain on dialysis indefinitely. Over the past few years, promising desensitization protocols have been developed that permit positive-crossmatch transplantation. These protocols include treatment with high doses of intravenous immunoglobulin, anti-CD20 antibodies, T-cell depletion strategies, plasma cell depletion, plasmapheresis, and complement blockade (1). An alternative approach has been developed in Sweden by Olausson et al. (2) and is based on combined auxiliary liver-kidney transplantation (3). The auxiliary liver from the same donor as the kidney is transplanted before the kidney transplantation with the purpose of protecting it form hyperacute rejection. This procedure might raise ethical questions of organ allocation. Nevertheless, none of the 10 transplanted patients hyperacutely rejected their kidney. The auxiliary liver did not prevent alloreactivity because 6 of 10 patients had an acute rejection episode, and 2 of these 6 patients lost their kidney allograft (3). One of the failed kidneys developed untreatable graft function deterioration after a complication that led to the removal of the auxiliary liver, suggesting a protective liver effect. An explanation for the relatively good results seen in this study is that the liver absorbs the preformed antibodies against donor human leukocyte antigens, the so-called sponge theory. Certainly, donor-specific antibodies disappeared in some but not all patients. This observation suggests that other mechanisms contribute to the protective role of auxiliary liver. In this issue of Transplantation, Ingelsten et al. (3) report on other mechanism. Liver-induced kidney graft acceptance is associated with an inflammatory liver response. Within hours after transplantation, the grafted liver but not the transplanted kidney was infiltrated with recipient CD3+ T cells and CD68+ macrophages and showed increased expression of nuclear factor κB-associated genes and indoleamine 2,3-dioxygenase. This enzyme is overexpressed in response to proinflammatory cytokines such as interferon-γ and may cause immunosuppression through breakdown of tryptophan in the liver microenvironment (3). Interestingly, the inflammatory response was particularly seen in livers of patients who did not acutely reject the transplanted kidney. This once again shows that immune activation is required to initiate responses that are key for donor-specific immunologic quiescence. In that hypothesis, the CCL20 findings nicely fit. It is intriguing that in the auxiliary liver of nonrejectors, the nuclear factor κB-dependent chemokine CCL20 is strongly up regulated. CCL20 is chemotactic for T cells including inflammatory T helper 17 cells and regulatory FoxP3+ T cells, B cells, and dendritic cells, and weakly for neutrophils (4). Thus, shortly after transplantation, the liver consists of chemokines that attract functionally different immune cells, is not rejected, and prevents the transplanted kidney from acute rejection. Therefore, FoxP3+ T cells might have infiltrated the liver and suppress the inflammatory activities of effector T cells. For instance, during acute rejection, FoxP3+ T cells home in the transplanted organ and effectively control aggressive intragraft antidonor immune reactivity (5). Furthermore, it could well be that in the auxiliary liver, other cell populations are present that inhibit inflammatory responses. Regulatory macrophages and natural killer cells have been identified that by themselves or in combination with liver-specific populations such as Kupffer cells contribute to the observed phenomenon. Overall, the data suggest that the transplanted auxiliary liver dampens the antidonor kidney response by a cascade of different mechanisms starting with the absorption of preexisting antidonor antibodies followed by indoleamine 2,3-dioxygenase activation and regulation by liver specific cells and FoxP3+ T cells. What is needed now is proof of principle: analysis of the T-cell compartment. What is the role of the observed T-cell infiltrate in the prevention of alloreactivity (3)? Are both effector T cells and suppressive FoxP3+ T cells present in the auxiliary liver? What is the specificity of the T cells? If indeed FoxP3+ regulatory T cells are involved in the control of immune responses, it might open the door for regulatory T-cell promoting drugs such as rapamycin, or even cell-based induction therapy in highly sensitized patients on the wait list. The unique setting of auxiliary liver-kidney transplantation provides the rare opportunity to study the mechanisms by which the human immune system suppresses aggressive alloreactivity.

Use of Intravenous Immune Globulin and Rituximab for Desensitization of Highly Human Leukocyte Antigen-Sensitized Patients Awaiting Kidney Transplantation

The article by Vo et al. (1) about transplanting highly sensitized patients is one of their most recent contributions in trying to tackle this recalcitrant problem. The authors used a rituximab and intravenous immune globulin desensitization protocol, which is simple to administer. This, however, together with the fact that the Cedars-Sinai group is well respected and that the protocol is proposed for highly human leukocyte antigen-sensitized patients (as shown in the title) is promoting its use worldwide with no results to justify the expense. Their definition of “highly sensitized” patients by flow panel reactive antibody is questionable. This test is sensitive but can give high percentage values with low or no sensitization (in contrast to the traditional cytotoxicity panel reactive antibody where high values usually go together with high titers). In addition, they do acknowledge that a number of their transplanted patients had flow crossmatches of less than 250 mean channel shifts, which they defined as “acceptable positive.” Many centers transplant these patients with increased immunosuppression but no desensitization. The authors mention that in some cases, patients received the treatment but the donor-specific crossmatch with the pretransplant specimen turned out to be low by chance. True, but this is certainly not a case of success because of the protocol. The authors also state that they would not transplant such patients without using their protocol, but they have not shown that patients with a weakly positive flow crossmatch do better with the protocol than without. Thus, it is not clear from the data how many patients would have had acceptable positive crossmatches before desensitization, or how many patients were treated and not transplanted. In addition, the effect of rituximab itself on alloantibody, and its indications in transplant patients, has not been established, as one of the authors acknowledged recently (2). Although a strict quantitative evaluation on the effect of rituximab plus intravenous immune globulin on human leukocyte antigen antibody levels remains to be done, the patients transplanted were obviously not highly sensitized against their donors. Indeed, at the end of the discussion, the authors themselves state that patients with lower donor-specific antibody levels benefit more and that no protocol deals well with highly sensitized patients. Some readers may miss this statement, but no one will miss the title. In summary, it has to be made clear that this protocol does not represent a solution for highly sensitized patients. Shehzad Rehman1 Herwig-Ulf Meier-Kriesche1 Juan Scornik2 1 Department of Medicine University of Florida Gainesville, FL 2 Department of Pathology University of Florida Gainesville, FL

Rises and Falls in Donor-Specific and Third-Party HLA Antibody Levels After Antibody Incompatible Transplantation

After human leukocyte antigen (HLA) antibody-incompatible transplantation, donor specific and third party HLA antibodies may be found, and their levels fall in a donor-specific manner during the first month. However, these changes have not been previously described in detail. Donor-specific HLA antibody (DSA) and third-party HLA antibody (TPA) levels were measured using the microbead method in 44 presensitized patients who had renal transplantation. DSA+TPA fell in the first 4 days after transplantation, and greater falls in DSA indicated absorption by the graft. This occurred for class I (57.8% fall compared with 20.2% for TPA, P<0.0005), HLA DR (63.0% vs. 24.3%, P<0.0004), and for HLA DP/DQ/DRB3-4 (34% vs. 17.5%, P=0.014). Peak DSA levels occurred at a mean of 13 days posttransplant, and they were higher than pretreatment in 25 (57%) patients and lower in 19 (43%) patients (P=ns). The risk of rejection was associated with peak DSA levels; 15 of 25 (60%) patients with DSA at median fluorescence intensity (MFI) more than 7000U experienced rejection, compared with 4 of 7 (57%) patients with peak DSA MFI 2000 to 7000U, and 2 of 12 (17%) patients with peak DSA MFI less than 2000U (P<0.02). DSA levels subsequently fell in a donor specific manner compared to TPA. DSA levels may change markedly in the first month after antibody incompatible transplantation, and the risk of rejection was associated with higher pretreatment and peak levels.

How Much Donor Human Leukocyte Antigen-Specific Antibody Is Too Much for a Renal Transplant?

How Much Donor Human Leukocyte Antigen-Specific Antibody Is Too Much for a Renal Transplant?

The association of class I HLA alleles and antibody levels after a single dose of measles vaccine

Despite the success of the current measles vaccine in controlling disease in industrialized countries, the importance of vaccine failure has become increasingly apparent. Our objective was to determine if associations exist between seronegativity after measles vaccination and class I human leukocyte antigen (HLA) alleles. We undertook a cross-sectional observational study in Rochester, Minnesota, with 242 school-age children previously recruited from a communitywide seroprevalence study. We studied two groups of subjects: 72 were seronegative (EIA ≤0.8 after a single dose of measles vaccine) and 170 were seropositive (enzyme immunoassy [EIA] ≥1.0 after one dose). We used the resources of Mayo Clinic’s tissue typing laboratory for serotyping class I HLA-A and HLA-B alleles via microlymphocytotoxicity assays. We found no statistically significant associations with class I HLA-A but did find associations with class I HLA-B, which includes alleles associated with seronegativity (B8, B13, and B44) and those associated with seropositivity (B7 and B51). Elucidation of the specific peptide-HLA complex interactions that lead to varying or failed immune responses may provide fertile groundwork for improved vaccines that can overcome limitations of the current live, attenuated measles vaccine.

Associations between human leukocyte antigen homozygosity and antibody levels to measles vaccine.

The association between human leukocyte antigen (HLA) homozygosity and measles antibody levels was assessed in a volunteer group of 242 children. Serum samples were tested for measles IgG antibodies, class I and class II HLA alleles were typed, and associations were examined between HLA homozygosity and antibody levels. Children who were homozygous for at least 1 locus were twice as likely to be seronegative (odds ratio, 1.97; 95% confidence interval, 1.08-3.61). Children who were homozygous at >/=1 loci were increasingly likely to be seronegative (chi(2) test for trend; P=.02). When serum antibody levels were examined as continuous variables, children who were homozygous at certain loci tended to have lower mean antibody levels. These results suggest that lack of HLA diversity may limit the range of peptides that can be presented to antibody-producing cells, potentially resulting in a decreased immune response to viral infections.