Evaluating the Clinical Relevance of Antibodies against Non-Human Leukocyte Antigen in Kidney Transplantation.

Introduction: Kidney transplantation is the preferred modality of kidney replacement therapy for eligible patients with end-stage kidney disease (ESKD), given that it has been found to reduce mortality rates, improve quality of life, and is cost-effective compared to dialysis. Recent advancements in human leukocyte antigen (HLA) typing and donor-specific antibody (DSA) detection have helped to reduce the risk of rejection, but antibody-mediated rejection (AMR) can still occur without DSA. Previous studies suggest that rejection can be attributed to antibodies against Non-Human Leucocyte Antigens (non-HLAs). We aimed to acquire further understanding of the prevalence and distribution of non-HLA antibodies in our local population and attempt to correlate these findings with graft outcomes, as well as assess whether non-HLA antibodies can be utilized to determine graft impairment and dysfunction. Methods: We conducted a retrospective study involving kidney transplant recipients between January 2010 and December 2020. All included individuals were aged over 18 and underwent kidney-alone transplants; were ABO- and HLA-compatible; and were matched at A, B, and DR loci (mismatch 0:0:0). HLA testing was negative at the time of transplantation. The samples from both cases of early graft rejection and the control group were tested for non-HLA antibodies using One Lambda LABScreenTM, Autoantibody kit groups 1, 2, and 3, as well as the Immucor LIFECODES non-HLA autoantibody assay. Results: A total of 850 kidney transplant recipients were included, in which 12 patients experienced early graft rejection within the first month post transplant and 18 patients who did not experience graft rejection were selected as study controls. Our study reported no correlation between the total burden of non-HLA antibodies and early rejection, most likely as the result of a small sample size. Nevertheless, a sub-analysis revealed that specific high-frequency pre-transplant non-HLA antibodies such as GSTT, CXCL11, CXCL10, and HNR, detected by LIFECODES, were associated with rejection (Fisher's exact test with Bonferroni correction, p < 0.001). Most pre-transplant non-HLA antibody levels were reduced after transplantation, which was attributed to immunosuppression. Conclusion: The 'high frequency' non-HLA antibodies displayed an association with graft rejection, though the overall associations between the burden of non-HLA antibodies and rejection episodes remain inconclusive. Further work is needed to establish the rebound phenomenon of non-HLA antibodies, the development of de novo non-HLA antibodies in the long run, and their implications on graft survival.

Homozygous HLA-DQB1*06:02 combined with T-cell receptor alpha polymorphism results in narcolepsy onset - A familial case report.

Narcolepsy is a life-long neurological disorder with well-established genetic risk factors. Human leukocyte antigen-DQB1*06:02 remains the strongest genetic predeterminant; however, polymorphisms in genes encoding the T-cell receptor alpha chain are also strongly linked. This case report shows the inheritance pathway of these genetic markers contributing to narcolepsy onset in a 17-year-old female.

Predicting flow cytometry crossmatch results from single-antigen bead testing.

The aim of this study was to devise an algorithm that would predict flow cytometry crossmatch (FCXM) results using single-antigen bead (SAB) mean fluorescent intensity (MFI) levels using samples received through the National External Quality Assurance Scheme (NEQAS) 2B external proficiency testing scheme between 2019 and 2023. A total of 159 serum samples were retrospectively screened using LABScreen Single Antigen Class I and II (SAB), and 40 peripheral blood samples were human leucocyte antigen (HLA) typed with LABType SSO. Donor-specific antibodies were identified for each cell-serum combination tested, and cumulative MFI values were calculated for each test before correlating the screening result with the consensus crossmatch results for this scheme. HLA Class I MFIs were combined to predict the T cell crossmatch. For the B cell crossmatch prediction, two options were considered: (i) HLA Class II MFI values alone and (ii) HLA Class I + Class II MFIs. Receiver operating characteristic analysis was carried out to identify the combined MFI threshold that predicted NEQAS consensus results with the greatest sensitivity and specificity. HLA Class I combined MFI >5000 predicted T cell crossmatch results with 96% sensitivity, 100% specificity, 100% positive predictive value (PPV) and 92% negative predictive value (NPV). For B cell results, HLA Class I + Class II combined MFIs >11,000 gave the best model, showing 97% sensitivity, 82% specificity, 96% PPV and 85% NPV. However, for samples with only HLA Class II sensitization, combined MFIs >13,000 improved the B cell crossmatch predictions: 92% sensitivity, 95% specificity, 96% PPV and 91% NPV. Using this model, combined MFI can be used to predict the immunological risk posed by donor-specific antibodies when it is not possible to carry out an FCXM.

Donor KIR2DL1 Allelic Polymorphism Influences Posthematopoietic Progenitor Cell Transplantation Outcomes in the T Cell Depleted and Reduced Intensity Conditioning Setting.

The majority of established KIR clinical assessment algorithms used for donor selection for hematopoietic progenitor cell transplantation (HPCT) evaluate gene content (presence/absence) of the KIR gene complex. In comparison, relatively little is known about the impact of KIR allelic polymorphism. By analyzing donors of T cell depleted (TcD) reduced intensity conditioning (RIC) HPCT, this study investigated the influence on post-transplant outcome of 2 polymorphic residues of the inhibitory KIR2DL1. The aim of this study was to expand upon existing research into the influence of KIR2DL1 allelic polymorphism upon post-transplant outcome. The effects of allele groups upon transplant outcomes were investigated within a patient cohort using a defined treatment protocol of RIC with TcD. Using phylogenetic data, KIR2DL1 allelic polymorphism was categorized into groups on the basis of variation within codons 114 and 245 (positive or negative for the following groups: KIR2DL1*002/001g, KIR2DL1*003, KIR2DL1*004g) and the identification of null alleles. The influence of these KIR2DL1 allele groups in hematopoietic progenitor cell transplantation (HPCT) donors was assessed in the post-transplant data of 86 acute myelogenous leukemia patients receiving RIC TcD HPCT at a single center. KIR2DL1 allele groups in the donor significantly impacted upon 5-year post-transplant outcomes in RIC TcD HPCT. Donor KIR2DL1*003 presented the greatest influence upon post-transplant outcomes, with KIR2DL1*003 positive donors severely reducing 5-year post-transplant overall survival (OS) compared to those receiving a transplant from a KIR2DL1*003 negative donor (KIR2DL1*003 pos versus neg: 27.0% versus 60.0%, P = .008, pc = 0.024) and disease-free survival (DFS) (KIR2DL1*003 pos versus neg: 23.5% versus 60.0%, P = .004, pc = 0.012), and increasing 5-year relapse incidence (KIR2DL1*003 pos versus neg: 63.9% versus 27.2%, P = .009, pc = 0.027). KIR2DL1*003 homozygous and KIR2DL1*003 heterozygous grafts did not present significantly different post-transplant outcomes. Donors possessing the KIR2DL1*002/001 allele group were found to significantly improve post-transplant outcomes, with donors positive for the KIR2DL1*004 allele group presenting a trend towards improvement. KIR2DL1*002/001 allele group (KIR2DL1*002/001g) positive donors improved 5-year OS (KIR2DL1*002/001g pos versus neg: 56.4% versus 27.2%, P = .009, pc = 0.024) and DFS (KIR2DL1*002/001g pos versus neg: 53.8% versus 25.5%, P = .018, pc = 0.036). KIR2DL1*004 allele group (KIR2DL1*004g) positive donors trended towards improving 5-year OS (KIR2DL1*004g pos versus neg: 53.3% versus 35.5%, P = .097, pc = 0.097) and DFS (KIR2DL1*004g pos versus neg: 50.0% versus 33.9%, P = .121, pc = 0.121), and reducing relapse incidence (KIR2DL1*004g pos versus neg: 33.1% versus 54.0%, P = .079, pc = 0.152). The presented findings suggest donor selection algorithms for TcD RIC HPCT should consider avoiding KIR2DL1*003 positive donors, where possible, and contributes to the mounting evidence that KIR assessment in donor selection algorithms should reflect the conditioning regime protocol used.

Immunology of cord blood T-cells favors augmented disease response during clinical pediatric stem cell transplantation for acute leukemia.

Allogeneic hematopoietic stem cell transplantation (HSCT) has been an important and efficacious treatment for acute leukemia in children for over 60 years. It works primarily through the graft-vs.-leukemia (GVL) effect, in which donor T-cells and other immune cells act to eliminate residual leukemia. Cord blood is an alternative source of stem cells for transplantation, with distinct biological and immunological characteristics. Retrospective clinical studies report superior relapse rates with cord blood transplantation (CBT), when compared to other stem cell sources, particularly for patients with high-risk leukemia. Xenograft models also support the superiority of cord blood T-cells in eradicating malignancy, when compared to those derived from peripheral blood. Conversely, CBT has historically been associated with an increased risk of transplant-related mortality (TRM) and morbidity, particularly from infection. Here we discuss clinical aspects of CBT, the unique immunology of cord blood T-cells, their role in the GVL effect and future methods to maximize their utility in cellular therapies for leukemia, honing and harnessing their antitumor properties whilst managing the risks of TRM.

Granulocyte transfusion during cord blood transplant for relapsed, refractory AML is associated with massive CD8+ T-cell expansion, significant cytokine release syndrome and induction of disease remission.

In high-risk myeloid malignancy, relapse is reduced using cord blood transplant (CBT) but remains the principal cause of treatment failure. We previously described T-cell expansion in CBT recipients receiving granulocyte transfusions. We now report the safety and tolerability of such transfusions, T-cell expansion data, immunophenotype, cytokine profiles and clinical response in children with post-transplant relapsed acute leukaemia who received T-replete, HLA-mismatched CBT and pooled granulocytes within a phase I/II trial (ClinicalTrials.Gov NCT05425043). All patients received the transfusion schedule without significant clinical toxicity. Nine of ten patients treated had detectable measurable residual disease (MRD) pre-transplant. Nine patients achieved haematological remission, and eight became MRD negative. There were five deaths: transplant complications (n = 2), disease (n = 3), including two late relapses. Five patients are alive and in remission with 12.7 months median follow up. Significant T-cell expansion occurred in nine patients with a greater median lymphocyte count than a historical cohort between days 7-13 (median 1.73 × 109 /L vs. 0.1 × 109 /L; p < 0.0001). Expanded T-cells were predominantly CD8+ and effector memory or TEMRA phenotype. They exhibited markers of activation and cytotoxicity with interferon-gamma production. All patients developed grade 1-3 cytokine release syndrome (CRS) with elevated serum IL-6 and interferon-gamma.

Understanding the killer-cell immunoglobulin like receptor polymorphism in retinoblastoma.

BACKGROUND: The KIR receptors present on the natural killer (NK) cells play a crucial role by exercising cytotoxicity to eliminate tumor cells. Both KIR and class-I HLA molecules exhibit extensive polymorphism. Although RB1 inactivation triggers the initiation of retinoblastoma; however additional immune alterations trigger tumor development. The aim was to explore the KIR/HLA polymorphism and its role in the pathogenesis of retinoblastoma. METHODS: Patients with unilateral, non-familial retinoblastoma were enrolled as cases. Healthy individuals matched for ethnicity were enrolled as controls. KIR genotyping was performed by sequence-specific primer assay. The investigated KIR genes included: inhibitory (2DL1, 2DL2, 2DL3, 2DL4, 2DL5A, 2DL5B), activating (2DS1, 2DS2, 2DS3, 2DS4*FUL, 2DS4*DEL, 2DS5, 3DL1, 3DL2, 3DL3, 3DS1) and pseudogenes (2DP1, 3DP1*FUL, 3DP1*DEL). In addition, HLA ligands were investigated by sequence-specific oligonucleotide assay for HLA-A, B, and C locus. RESULTS: KIR genotyping was performed in 48 cases and 107 controls. The mean age of cases was 2.9 ± 2.2 years (range: 0.25-10). Among the 19 KIR genes, the frequency of KIR2DS4*FUL (p = 0.0019) and 2DS5 (p = 0.0095) was increased among cases. HLA ligands were investigated in 25 cases and 50 controls. The frequency of HLA ligands (C1/C2, Bw4, A3/A11) was similar among cases and controls. However, the KIR/HLA combination frequency for KIR3DS1/HLA-Bw4 was decreased in cases (p = 0.006). CONCLUSION: It is the pioneer study to report the association of killer cell immunoglobulin-like receptors in retinoblastoma. KIR2DS4*FUL and KIR2DS5 had a susceptible, and KIR3DS1/HLA-BW4 had a protective role in retinoblastoma. The results will aid in exploring the therapeutic potential of NK cell-based therapy for retinoblastoma.

An early evaluation of the HISTO SPOT® AB ID Class I & II test in cardiothoracic transplant patients.

The HISTO SPOT® AB ID assay (BAG Diagnostics GmbH) is a novel single antigen HLA Class I & II antibody definition test used with the MR.SPOT® processor. We compared this assay with Luminex® -based assays to assess its potential application in defining unacceptable antigens for transplantation in patients awaiting transplants with cardiothoracic organs. A cohort of 40 sensitized cardiothoracic patients were identified, and one sample was selected from each patient. The required screening was based on the patients' antibody profiles (Class I, n = 17, Class II, n = 11, Class I & II, n = 12). Samples were screened with LABScreen™ Single Antigen (SAg), LIFECODES® LSA™, HISTO SPOT® AB ID, and an acid modified LABScreen™ SAg test for detecting antibodies against denatured HLA. Results indicated that HISTO SPOT® AB ID had reduced sensitivity (68% for Class I; 69% for Class II). When compared to LABScreen™ and LIFECODES® , HISTO SPOT® AB ID failed to detect Luminex® -defined antibodies with median fluorescence intensity (MFI) ranging from 1114 to 24,489. The HISTO SPOT® AB ID panel used in the study had reduced antigen representation compared with Luminex® -based assays which further compromised its capacity for antibody detection and definition. Further work is needed to evaluate the clinical relevance of these differences between the performance of HISTO SPOT® and Luminex® -based methods.

Strategies for Success With Umbilical Cord Haematopoietic Stem Cell Transplantation in Children With Malignant and Non-Malignant Disease Indications.

Umbilical Cord blood is an intuitively attractive stem cell source, but its use has declined since it is associated with an increased procedure-related morbidity and transplant related mortality. Some of this reflects that cord blood transplants are more often HLA-mismatched compared to other unrelated donor transplants. The ability to transplant in such a setting, indeed without high rates of chronic Graft versus Host Disease (GVHD), constitutes an advantage compared to other unrelated donor cell sources and there are other advantages specifically associated with cord blood as a donor cell source. These advantages must be weighed against its disadvantage, and we have utilised cord blood preferentially as a donor cell source in certain clinical situations in paediatric medicine. In non-malignant diseases, outcomes in metabolic disease are critically dependent on age at transplant and the enzyme delivered by that transplant, and in cord blood transplantation then the time to transplant can be minimised and the engrafted recipients have higher chimerism that delivers higher enzyme levels. In malignant diseases, studies have described reduced relapse rate and better GVHD-free survival, and so we have prioritised cord as a donor cell source where the risk of relapse is highest, and the effects of higher transplant related mortality is most clearly offset by the reduced relapse rates.

Systematic review of associations between HLA and renal function.

INTRODUCTION: Kidney dysfunction is a highly significant disease, both in the United Kingdom and globally. Many previous studies have reported associations between human leukocyte antigens (HLA) and renal function; this systematic review attempts to identify, summarize and appraise all published studies of these associations. METHODS: A literature search was performed using Medline, Embase and Cochrane Central Register of Controlled Trials to identify papers whose keywords included each of the following concepts: HLA, renal failure and genetic association. A total of 245 papers were identified and assessed for eligibility; 35 of these were included in the final study. RESULTS: A total of 95 HLA types and 14 three-locus haplotypes were reported to be associated with either increased or decreased renal function. A number of these findings were replicated by independent studies that reported 16 types were protective against renal dysfunction and 15 types were associated with reduced renal function. A total of 20 HLA types were associated with both increased risk of renal disease and decreased risk by independent studies. DISCUSSION: There is very little consensus on which HLA types have a protective or deleterious effect on renal function. Ethnicity may play a role, with HLA types possibly having different effects among different populations, and it is possible that the different primary diseases that lead to ESRD may have different HLA associations. Some of the studies may contain type I and type II errors caused by insufficient sample sizes, cohort selection and statistical methods. Although we have compiled a comprehensive list of published associations between renal function and HLA, in many cases, it is unclear which associations are reliable. Further studies are required to confirm or refute these findings.

Human leukocyte antigen epitope mismatch loads and the development of de novo donor-specific antibodies in cardiothoracic organ transplantation.

De novo donor-specific human leucocyte antigen (HLA) antibodies (dnDSA) are associated with increased risk of rejection and mortality in solid organ transplantation. Such dnDSA is produced in some recipients upon allorecognition of mismatched HLA post-transplant. HLA matching is not currently considered in the allocation of deceased donor hearts and lungs and pre-transplant immunological risk stratification is based entirely on the mean fluorescence intensity (MFI) of circulating donor-directed HLA antibodies. HLA epitope-based matching tools predict B-cell or T-cell HLA epitopes that are present in the donor's HLA but absent in the recipient's HLA. We hypothesized that patients with higher epitope mismatch loads would be at increased risk of dnDSA development. We retrospectively analysed 73 heart and/or lung transplant recipients who were tested for DSA between 2015 and 2020. HLAMatchmaker, PIRCHE-II and HLA epitope mismatch algorithm (HLA-EMMA) were used to calculate eplet mismatch (EpMM) loads, T-cell epitope mismatch (TEpMM) loads and solvent accessible amino acid mismatch (SAMM) loads, respectively. Multivariate analyses showed that HLA-EMMA was the only tool with a significant association between the total score for all HLA loci and dnDSA production [odds ratio (OR) 1.021, 95% confidence interval (CI) 1.003-1.042, p = .0225] though this increased risk was marginal. The majority of dnDSA were directed against HLA-DQ and patients with higher HLA-DQ TEpMM loads (OR = 1.008, CI = 1.002-1.014, p = .007), and HLA-DR+DQ SAMM loads (OR = 1.035, CI = 1.010-1.064, p = .0077) were most at risk of producing dnDSA. We also showed that patients with a risk epitope within the HLA molecule encoded for by HLA-DQA1*05 + HLA-DQB1*02/03:01 were significantly more likely to produce dnDSA. The use of HLA epitope-based matching tools could be used for cardiothoracic transplant risk stratification to enable early intervention and monitoring of patients at increased risk of producing dnDSA.

BSHI guideline: HLA matching and donor selection for haematopoietic progenitor cell transplantation.

A review of the British Society for Histocompatibility and Immunogenetics (BSHI) Guideline 'HLA matching and donor selection for haematopoietic progenitor cell transplantation' published in 2016 was undertaken by a BSHI appointed writing committee. Literature searches were performed and the data extracted were presented as recommendations according to the GRADE nomenclature.

Associations between human leukocyte antigens and renal function.

Human leukocyte antigens (HLA) have been associated with renal function, but previous studies report contradictory findings with little consensus on the exact nature or impact of this observation. This study included 401,307 white British subjects aged 39-73 when they were recruited by UK Biobank. Subjects' HLA types were imputed using HLA*IMP:02 software. Regression analysis was used to compare 362 imputed HLA types with estimated glomerular filtration rate (eGFR) as a primary outcome and clinical indications as secondary outcome measures. 22 imputed HLA types were associated with increased eGFR (and therefore increased renal function). Decreased eGFR (decreased renal function) was associated with 11 imputed HLA types, seven of which were also associated with increased risk of end-stage renal disease and/or chronic kidney disease. Many of these HLA types are commonly inherited together in established haplotypes, for example: HLA-A*01:01, B*08:01, C*07:01, DRB1*03:01, DQB1*02:01. This haplotype has a population frequency of 9.5% in England and each allele was associated with decreased renal function. 33 imputed HLA types were associated with kidney function in white British subjects. Linkage disequilibrium in HLA heritance suggests that this is not random and particularly affects carriers of established haplotypes. This could have important applications for the diagnosis and treatment of renal disease and global population health.

Human leukocyte antigen associations with renal function among ethnic minorities in the United Kingdom.

Human leukocyte antigens (HLA) have been associated with renal function, but previous studies report contradictory findings. There has been a lack of research into how HLA affects renal function in Black, Asian and Minority Ethnic (BAME) people in the UK, despite BAME people being disproportionately affected by renal dysfunction. This study included >27 000 UK Biobank subjects of six ethnicities (>12 100 Irish, >5400 Indian, >4000 Black Caribbean, >3000 Black African, >1600 Pakistani, and >1400 Chinese) aged 39 to 73. Subjects' high-resolution HLA genotypes were imputed using HLA*IMP:02 software. Regression analysis was used to compare 108 imputed HLA alleles with two measures of estimated glomerular filtration rate (eGFR): one based on serum creatinine; one based on serum cystatin. Secondary analysis compared CKD stage 2 subjects to healthy controls. Nine imputed HLA alleles were associated with eGFR (adjusted P < .05). Six associations were based on creatinine in Black African subjects: HLA-B*53:01 (beta = -2.628, adjusted P = 4.69 × 10-4 ); C*04:01 (beta = -1.667, adjusted P = .0269); DPA1*02:01 (beta = -1.569, adjusted P = .0182); and DPA1*02:02 (beta = -1.716, adjusted P = .0251) were linked to decreased renal function, while DRB1*03:01 (beta = 3.200, adjusted P = 3.99 × 10-3 ) and DPA1*01:03 (beta = 2.276, adjusted P = 2.31 × 10-5 ) were linked to increased renal function. Two of these (HLA-B*53:01 and C*04:01) are commonly inherited together. In Irish subjects, HLA-DRB1*04:01 (beta = 1.075, adjusted P = .0138) was linked to increased eGFR (based on cystatin); in Indian subjects, HLA-DRB1*03:01 (beta = -1.72, adjusted P = 4.78 × 10-3 ) and DQB1*02:01 (beta = -1.755, adjusted P = 2.26 × 10-3 )were associated with decreased eGFR (based on cystatin). No associations were found in the other three ethnic groups. Nine HLA alleles appear to be associated with kidney function in BAME people in the UK. This could have applications for the diagnosis and treatment of renal disease and could help reduce health inequalities in the UK.

Cord blood CD8+ T-cell expansion following granulocyte transfusions eradicates refractory leukemia.

The action of hematopoietic cell transplantation in controlling leukemia is principally mediated by donor T cells directed against residual recipient malignant cells. However, its utility is limited by graft-versus-host disease (GVHD), where alloreactivity is extended beyond leukemic and marrow cells. In a human/murine chimeric model, we previously showed that the preferential infiltration of cord blood (CB) CD8+ T cells eradicates an Epstein-Barr virus-driven lymphoblastoid tumor without causing xenogeneic GVHD. In the clinic, however, cord blood CD8+ T-cell reconstitution is significantly delayed, and the observation of such a robust antileukemia effect mediated by cord blood CD8+ T cells has not been reported. We describe an observation of very early T-cell expansion in 4 high-risk pediatric leukemia patients receiving third-party, pooled granulocytes after T cell-replete CB transplantation (CBT). The T-cell expansion was transient but robust, including expansion of CD8+ T cells, in contrast to the delayed CD8+ T-cell expansion ordinarily observed after T cell-replete CBT. The CD8+ T cells were polyclonal, rapidly switched to memory phenotype, and had the ability to mediate cytotoxicity. This phenomenon is reproducible, and each patient remains in long-term remission without GVHD. The results suggest that fetal-derived CB CD8+ T cells can be exploited to generate robust antileukemia effects without GVHD.

A role for human leucocyte antigens in the susceptibility to SARS-Cov-2 infection observed in transplant patients.

We analysed data from 80 patients who tested positive for SARS-CoV-2 RNA who had previously been HLA typed to support transplantation. Data were combined from two adjacent centres in Manchester and Leeds to achieve a sufficient number for early analysis. HLA frequencies observed were compared against two control populations: first, against published frequencies in a UK deceased donor population (n = 10,000) representing the target population of the virus, and second, using a cohort of individuals from the combined transplant waiting lists of both centres (n = 308), representing a comparator group of unaffected individuals of the same demographic. We report a significant HLA association with HLA- DQB1*06 (53% vs. 36%; p < .012; OR 1.96; 95% CI 1.94-3.22) and infection. A bias towards an increased representation of HLA-A*26, HLA-DRB1*15, HLA-DRB1*10 and DRB1*11 was also noted but these were either only significant using the UK donor controls, or did not remain significant after correction for multiple tests. Likewise, HLA-A*02, HLA-B*44 and HLA-C*05 may exert a protective effect, but these associations did not remain significant after correction for multiple tests. This is relevant information for the clinical management of patients in the setting of the current SARS-CoV-2 pandemic and potentially in risk-assessing staff interactions with infected patients.

SARS-CoV-2: An immunogenetics call to arms.

Susceptibility to viral infection, development of immunity, response to treatment and patient clinical outcomes are all under the control of heritable factors in the host. In the context of the current SARS-Cov-2 pandemic, this review considers existing immunogenetic knowledge of virus-immune system interactions. A major focus is to highlight areas in which work is required in order to improve understanding of antiviral immune responses and to move towards improved patient management.

HLA-C expression level in both unstimulated and stimulated human umbilical vein endothelial cells is defined by allotype.

Human leukocyte antigens (HLA) are present on the surface of all nucleated cells, with the level of expression dependent on the particular HLA locus, the cell type and cellular activation state. Human umbilical vein endothelial cells (HUVECs) are easily isolated from umbilical cords and may aid our understanding of HLA expression on the vascular endothelium in the setting of transplantation. Endothelial cells on the donor-recipient interface form the barrier between transplanted organs and the host immune system. Increased knowledge of the variation in levels of individual HLA specificities may inform the assessment of transplant risk. HUVECs from 48 full term babies born consecutively following planned caesarean section were isolated, HLA typed and grown on gelatin coated culture wells. Once confluent, cells were stimulated with optimal concentrations of the cytokines TNF-α and IFN-γ for 24 hours and HLA-C expression on both unstimulated and stimulated cells was quantified by flow cytometry using the fluorescent labelled monoclonal antibody DT-9 PE. Unstimulated HLA-C expression varied by over 60% between allotypes (ANOVA, P = .004). Following stimulation, HLA-C levels increased over 15-fold and showed the same variation of expression between allotypes (P < .001). Cell surface HLA-C expression increases between 500% and 3125%, after stimulation for 24 hours. HLA-C level varies between allotypes and cells expressing more HLA-C at baseline tended to have corresponding higher levels of HLA-C following cytokine stimulation (Pearson's correlation coefficient between unstimulated and stimulated expression, P = .002).

HLA expression levels of unstimulated and cytokine stimulated human umbilical vein endothelial cells.

Transplant rejection occurs following recipient recognition of mismatched HLA on donor tissue, but active rejection is dependent not only upon the severity of the T cell or alloantibody response, but also upon the cell surface expression of target HLA molecules. To investigate the variation in HLA expression using a model of endothelium, human umbilical vein endothelial cell (HUVEC) cultures were generated from 48 umbilical cords donated consecutively following planned caesarean section. HUVECs were stimulated using the cytokines tumour necrosis factor alpha and interferon gamma and HLA expression of unstimulated and stimulated cells determined using flow cytometry. HLA-A2, HLA-A3 and HLA-C antigens all showed a modest increase in expression for 12 hours post cell activation, followed by a more pronounced response over the next 24 to 36 hours. Each of these antigens increased by up to 40 times over unstimulated levels and in addition cells homozygous for specific HLA antigens on average had twice the amount of antigen expressed compared with cells heterozygous for that antigen, both when unstimulated and following cytokine stimulation. Cell activation is an important consideration in the assessment of transplant risk and may help progress towards understanding why rejection does not always occur in the presence of significant donor specific antibody. This data also confirms guidelines for transplantation, which recommend doubling the specific antibody level when considering immunological risk for homozygous donors.

Monthly variance in UK renal transplantation activity: a national retrospective cohort study.

OBJECTIVE: To identify whether renal transplant activity varies in a reproducible manner across the year. DESIGN: Retrospective cohort study using NHS Blood and Transplant data. SETTING: All renal transplant centres in the UK. PARTICIPANTS: A total of 24 270 patients who underwent renal transplantation between 2005 and 2014. PRIMARY OUTCOME: Monthly transplant activity was analysed to see if transplant activity showed variation during the year. SECONDARY OUTCOME: The number of organs rejected due to healthcare capacity was analysed to see if this affected transplantation rates. RESULTS: Analysis of national transplant data revealed a reproducible yearly variance in transplant activity. This activity increased in late autumn and early winter (p=0.05) and could be attributed to increased rates of living (October and November) and deceased organ donation (November and December). An increase in deceased donation was attributed to a rise in donors following cerebrovascular accidents and hypoxic brain injury. Other causes of death (infections and road traffic accidents) were more seasonal in nature peaking in the winter or summer, respectively. Only 1.4% of transplants to intended recipients were redirected due to a lack of healthcare capacity, suggesting that capacity pressures in the National Health Service did not significantly affect transplant activity. CONCLUSION: UK renal transplant activity peaks in late autumn/winter in contrast to other countries. Currently, healthcare capacity, though under strain, does not affect transplant activity; however, this may change if transplantation activity increases in line with national strategies as the spike in transplant activity coincides with peak activity in the national healthcare system.