The detection of antibodies against the human leukocyte antigen (HLA) complex has become indispensable in every clinical practice. The development of solid-phase assays like the Luminex allows the standardized measurement of anti-HLA antibodies (HLAab) with high sensitivity, albeit the relevance for some clinical settings remains a matter of debate. In this review we aim to describe the principle of Luminex-based antibody detection, including two modifications that allow identifying solely complement-activating antibodies. We then describe three applications for Luminex: i) detection of HLAab preceding solid-organ transplantation and monitoring of donor-specific antibodies posttransplant as a risk factor for antibody-mediated rejection; ii) presence of HLAab in recipients as a risk for graft failure in hematopoietic stem cell transplantation, especially in haploidentical or mismatched transplantations; iii) role of HLAab in blood transfusion including refractory thrombocytopenia and selection of suitable platelet donors, transfusion-related lung injury after plasma transfusion, and immunization against HLA after red blood cell transfusion despite leukodepletion. Although the Luminex platform constitutes a potent technology for HLA antibody detection, some drawbacks require the well-educated analysis and interpretation of data in critical cases. In addition, Luminex has become an important tool to identify clinically relevant antibodies.

C1q- and C4d-Luminex assays are characterized by an increased sensitivity and specificity compared with CDC, the current standard in detecting complement-fixing HLA antibodies. Pretransplantation risk assessment for transplantation but also posttransplantation monitoring are important applications for both assays to improve overall allograft survival.

ObjectiveTo study the B-cell content, organization, and existence of distinct B-cell subpopulations in relation to the expression of type 1 interferon signature related genes in dermatomyositis (DM).MethodsEvaluation of skeletal muscle biopsies from patients with adult DM (aDM) and juvenile DM (jDM) by histology, immunohistochemistry, electron microscopy, and quantitative reverse-transcription PCR.ResultsWe defined 3 aDM subgroups—classic (containing occasional B cells without clusters), B-cell–rich, and follicle-like aDM—further elucidating IM B-lymphocyte maturation and immunity. The quantity of B cells and formation of ectopic lymphoid structures in a subset of patients with aDM were associated with a specific profile of cytokines and chemokines involved in lymphoid neogenesis. Levels of type 1 interferon signature related gene expression paralleled B-cell content and architectural organization and link B-cell immunity to the interferon type I signature.ConclusionThese data corroborate the important role of B cells in DM, highlighting the direct link between humoral mechanisms as key players in B-cell immunity and the role of type I interferon–related immunity.

ObjectiveRefractory coeliac disease (RCD) is a potentially hazardous complication of coeliac disease (CD). In contrast to RCD type I, RCD type II is a precursor entity of enteropathy-associated T-cell lymphoma (EATL), which is associated with clonally expanding T-cells that are also found in the sequentially developing EATL. Using high-throughput sequencing (HTS), we aimed to establish the small-intestinal T-cell repertoire (TCR) in CD and RCD to unravel the role of distinct T-cell clonotypes in RCD pathogenesis.DesignDNA extracted from duodenal mucosa specimens of controls (n=9), active coeliacs (n=10), coeliacs on a gluten-free diet (n=9), RCD type I (n=8), RCD type II (n=8) and unclassified Marsh I cases (n=3) collected from 2002 to 2013 was examined by TCRβ-complementarity-determining regions 3 (CDR3) multiplex PCR followed by HTS of the amplicons.ResultsOn average, 106 sequence reads per sample were generated consisting of up to 900 individual TCRβ rearrangements. In RCD type II, the most frequent clonotypes (ie, sequence reads with identical CDR3) represent in average 42.6% of all TCRβ rearrangements, which was significantly higher than in controls (6.8%; p<0.01) or RCD type I (6.7%; p<0.01). Repeat endoscopies in individual patients revealed stability of clonotypes for up to several years without clinical symptoms of EATL. Dominant clonotypes identified in individual patients with RCD type II were unique and not related between patients. CD-associated, gliadin-dependent CDR3 motifs were only detectable at low frequencies.ConclusionsTCRβ-HTS analysis unravels the TCR in CD and allows detailed analysis of individual TCRβ rearrangements. Dominant TCRβ sequences identified in patients with RCD type II are unique and not homologous to known gliadin-specific TCR sequences, supporting the assumption that these clonal T-cells expand independent of gluten stimulation.

BackgroundNew strategies to optimize donor selection for hematopoietic stem cell transplantation (HSCT) have mainly been evaluated in adults, but the disease spectrum requiring HSCT differs significantly in children and has consequences for the risk of complications, such as graft‐versus‐host disease (GvHD).ProceduresHere we evaluated whether HLA‐DPB1 and Predicted Indirectly ReCognizable HLA‐Epitope (PIRCHE) matching can improve donor selection and minimize risks specific for a pediatric cohort undergoing HSCT in Berlin between 2014 and 2016.ResultsThe percentage of HLA‐DPB1–mismatched HSCT in the pediatric cohort was in line with the general distribution among matched unrelated donor HSCT. Nonpermissive HLA‐DPB1 mismatches were not associated with a higher incidence of GvHD, but the incidence of relapse was higher in patients undergoing HSCT from HLA‐DPB1–matched transplantations. High PIRCHE‐I scores were associated with a significantly higher risk for developing GvHD in patients undergoing HSCT from nine of ten matched unrelated donors. This finding persisted after including HLA‐DPB1 into the PIRCHE analysis.ConclusionsImplementing PIRCHE typing in the donor selection process for HSCT in children could particularly benefit children with nonmalignant diseases and support further validation of PIRCHE‐based donor selection in a larger number of children treated at different sites.