Frequency and Determinants of Pregnancy-Induced Child-Specific Sensitization

The aim of this study was to define the frequency and determinants of pregnancy-induced child-specific sensitization shortly after full-term delivery using sensitive single HLA-antigen beads (SAB) and high resolution HLA-typing of the mothers and their children (n = 301). A positive SAB result was defined by a background normalized ratio >1 or a mean fluorescence intensity (MFI) >300, >500 and >1000, respectively. The overall frequency of pregnancy-induced sensitization determined by SAB shortly after full-term delivery was between 45% (MFI > 1000 cut-off) and 76% (ratio cut-off). The rate of child-specific sensitization at the HLA-A/B/C/DRB1 loci was between 28% (MFI > 1000 cut-off) and 38% (ratio cut-off). The number of live birth was associated with a higher frequency of sensitization, which was driven by child-specific, but not third party HLA-antibodies. There was a clear hierarchy of sensitization among the investigated loci (B-locus: 31%; A-locus: 26%; DRB1-locus: 20%; C-locus: 15%; p < 0.0001). Some mismatched paternal HLA-antigens led to a significantly higher rate of sensitization than the average (e.g. HLA-A2, HLA-B49, HLA-B51, HLA-C*15). Furthermore, the mother's own HLA-phenotype—especially HLA-A/B homozygosity—was associated with a higher rate and broadness of sensitization. The number of mismatched HLA-A/B/C eplets strongly correlated with the rate of child-specific class I sensitization (read more)

Pretransplant Interferon-γ Secretion by CMV-Specific CD8+ T Cells Informs the Risk of CMV Replication After Transplantation

In this prospective study we analyzed pretransplant interferon-γ secretion by cytomegalovirus (CMV)-specific CD8+ T cells to assess its possible utility in determining the risk of CMV replication after solid organ transplantation. A total of 113 lung and kidney transplant patients were enrolled in the study but only 55 were evaluable. All CMV-seronegative recipients were pretransplant “nonreactive” (IFNγ <0.2 IU/mL) (11/11), whereas 30/44 (68.2%) CMV-seropositive (R+) recipients were “reactive” (IFNγ ≥0.2 IU/mL) and 14/44 (31.8%) were “nonreactive”. In the R(+) “nonreactive” group, 7/14 (50%) developed posttransplant CMV replication, whereas the virus replicated only in 4/30 (13.3%) of the R(+) “reactive” patients (p = 0.021). According to the best multivariate model, pretransplant “nonreactive” recipients receiving an organ from a CMV-seropositive donor had a 10-fold increased risk of CMV replication compared to pretransplant “reactive” recipients (adjusted OR 10.49, 95% CI 1.88–58.46). This model displayed good discrimination ability (AUC 0.80) and calibration (Hosmer–Lemeshow test, p = 0.92). Negative and positive predictive values were 83.7% and 75%, respectively. The accuracy of the model was 82%. Therefore, assessment of interferon-γ secretion by cytomegalovirus (CMV)-specific CD8+ T cells prior to transplantation is useful in informing the risk of posttransplant CMV replication in solid organ transplant patients (read more)

Correlation of Infused CD3+CD8+ Cells with Single-Donor Dominance after Double-Unit Cord Blood Transplantation

Single-donor dominance is observed in the majority of patients following double-unit cord blood transplantation (dCBT); however, the biological basis for this outcome is poorly understood. To investigate the possible influence of specific cell lineages on dominance in dCBT, flow cytometry assessment for CD34+, CD14+, CD20+, CD3−CD56+, CD3+CD56+ (natural killer), and T cell subsets (CD4+, CD8+, memory, naïve, and regulatory) was performed on individual units. Subsets were calculated as infused viable cells per kilogram of recipient actual weight. Sixty patients who underwent dCBT were included in the final analysis. Higher CD3+ cell dose was statistically concordant with the dominant unit in 72% of cases (P = .0006). Further T cell subset analyses showed that dominance was correlated more with the naive CD8+ cell subset (71% concordance; P = .009) than with the naive CD4+ cell subset (61% concordance; P = .19). These data indicate that a greater total CD3+ cell dose, particularly of naïve CD3+CD8+ T cells, may play an important role in determining single-donor dominance after dCBT (read more)

Allogeneic Transplantation: When is a Mismatch Better than a Match?

An accepted fact in allogeneic transplantation from unrelated donors, supported by multiple publications, including large numbers of transplantation patients, is that matching for human leukocyte antigen (HLA) is critical to ensure the best outcomes for patients. The current gold standard is an unrelated donor matched for 10/10 (or 8/8) HLA alleles (at HLA-A, -B, -C, -DRB1 +/− DQB1). Graft-versus-host disease (GVHD) is increased in the HLA-mismatched setting, and overall survival becomes significantly worse as the number of mismatched alleles at these loci increases  (read more)

Donor-Derived Mesenchymal Stem Cells Combined With Low-Dose Tacrolimus Prevent Acute Rejection After Renal Transplantation: A Clinical Pilot Study

 Background: The deleterious side effects of calcineurin inhibitors have impaired long-term survival after renal allograft. New immunotherapy regimens that minimize or even eliminate calcineurin inhibitors are required to improve transplantation outcome. Mesenchymal stem cells (MSCs) represent a unique cell population with immunosuppressive function and prolong allograft survival in experimental organ transplant models.
Methods: In this pilot study, donor-derived bone marrow MSCs combined with a sparing dose of tacrolimus (50% of standard dose) were administered to six de novo living-related kidney transplant recipients. Six other patients who received a standard dose of tacrolimus were enrolled as a control. The safety of MSC infusion, acute rejection, graft function, and patient and graft survival within 12 months after kidney transplantation were observed. The immune profiles were analyzed at different time points after transplantation.
Results: None of the MSC recipients experienced immediate or long-term toxic side effects associated with MSC infusion. The tacrolimus dose (0.045±0.002 mg/kg) in the MSC group was significantly reduced compared with the control group (0.077±0.005 mg/kg). One acute rejection occurred only in the control group. All patients survived with stable renal function at month 12 and no chimerism was detectable at month 3. Patients in the MSC group showed significantly higher B-cell levels than the control group at month 3.
Conclusion: These preliminary data suggest that the use of MSCs could provide potential benefits in renal transplantation by reducing the dosage of conventional immunosuppressive drug that is required to maintain long-term graft survival and function (read more)

Consensus Guidelines on the Testing and Clinical Management Issues Associated With HLA and Non-HLA Antibodies in Transplantation

Background: The introduction of solid-phase immunoassay (SPI) technology for the detection and characterization of human leukocyte antigen (HLA) antibodies in transplantation while providing greater sensitivity than was obtainable by complement-dependent lymphocytotoxicity (CDC) assays has resulted in a new paradigm with respect to the interpretation of donor-specific antibodies (DSA). Although the SPI assay performed on the Luminex instrument (hereafter referred to as the Luminex assay), in particular, has permitted the detection of antibodies not detectable by CDC, the clinical significance of these antibodies is incompletely understood. Nevertheless, the detection of these antibodies has led to changes in the clinical management of sensitized patients. In addition, SPI testing raises technical issues that require resolution and careful consideration when interpreting antibody results.
Methods: With this background, The Transplantation Society convened a group of laboratory and clinical experts in the field of transplantation to prepare a consensus report and make recommendations on the use of this new technology based on both published evidence and expert opinion. Three working groups were formed to address (a) the technical issues with respect to the use of this technology, (b) the interpretation of pretransplantation antibody testing in the context of various clinical settings and organ transplant types (kidney, heart, lung, liver, pancreas, intestinal, and islet cells), and (c) the application of antibody testing in the posttransplantation setting. The three groups were established in November 2011 and convened for a “Consensus Conference on Antibodies in Transplantation” in Rome, Italy, in May 2012. The deliberations of the three groups meeting independently and then together are the bases for this report.
Results: A comprehensive list of recommendations was prepared by each group. A summary of the key recommendations follows. Technical Group: (a) SPI must be used for the detection of pretransplantation HLA antibodies in solid organ transplant recipients and, in particular, the use of the single-antigen bead assay to detect antibodies to HLA loci, such as Cw, DQA, DPA, and DPB, which are not readily detected by other methods. (b) The use of SPI for antibody detection should be supplemented with cell-based assays to examine the correlations between the two types of assays and to establish the likelihood of a positive crossmatch (XM). (c) There must be an awareness of the technical factors that can influence the results and their clinical interpretation when using the Luminex bead technology, such as variation in antigen density and the presence of denatured antigen on the beads. Pretransplantation Group: (a) Risk categories should be established based on the antibody and the XM results obtained. (b) DSA detected by CDC and a positive XM should be avoided due to their strong association with antibody-mediated rejection and graft loss. (c) A renal transplantation can be performed in the absence of a prospective XM if single-antigen bead screening for antibodies to all class I and II HLA loci is negative. This decision, however, needs to be taken in agreement with local clinical programs and the relevant regulatory bodies. (d) The presence of DSA HLA antibodies should be avoided in heart and lung transplantation and considered a risk factor for liver, intestinal, and islet cell transplantation. Posttransplantation Group: (a) High-risk patients (i.e., desensitized or DSA positive/XM negative) should be monitored by measurement of DSA and protocol biopsies in the first 3 months after transplantation. (b) Intermediate-risk patients (history of DSA but currently negative) should be monitored for DSA within the first month. If DSA is present, a biopsy should be performed. (c) Low-risk patients (nonsensitized first transplantation) should be screened for DSA at least once 3 to 12 months after transplantation. If DSA is detected, a biopsy should be performed. In all three categories, the recommendations for subsequent treatment are based on the biopsy results.
Conclusions: A comprehensive list of recommendations is provided covering the technical and pretransplantation and posttransplantation monitoring of HLA antibodies in solid organ transplantation. The recommendations are intended to provide state-of-the-art guidance in the use and clinical application of recently developed methods for HLA antibody detection when used in conjunction with traditional methods (read more)

HLA Class II Molecules Influence Susceptibility versus Protection in Inflammatory Diseases by Determining the Cytokine Profile [BRIEF REVIEWS]

The MHC in humans encodes the most polymorphic genes, the HLA genes, which are critical for the immune system to clear infection. This can be attributed to strong selection pressure as populations moved to different parts of the world and encountered new kinds of infections, leading to new HLA class II alleles. HLA genes also have the highest relative risk for autoimmune diseases. Three haplotypes, that is, HLA-DR2DQ6, DR4DQ8, and DR3DQ2, account for HLA association with most autoimmune diseases. We hypothesize that these haplotypes, along with their multiple subtypes, have survived bottlenecks of infectious episodes in human history because of their ability to present pathogenic peptides to activate T cells that secrete cytokines to clear infections. Unfortunately, they also present self-peptides/mimics to activate autoreactive T cells secreting proinflammatory cytokines that cause autoimmune diseases (read more)