Gemcitabine Modulates HLA-I Regulation to Improve Tumor Antigen Presentation by Pancreatic Cancer Cells.

Pancreatic cancer is a lethal disease, harboring a five-year overall survival rate of only 13%. Current treatment approaches thus require modulation, with attention shifting towards liberating the stalled efficacy of immunotherapies. Select chemotherapy drugs which possess inherent immune-modifying behaviors could revitalize immune activity against pancreatic tumors and potentiate immunotherapeutic success. In this study, we characterized the influence of gemcitabine, a chemotherapy drug approved for the treatment of pancreatic cancer, on tumor antigen presentation by human leukocyte antigen class I (HLA-I). Gemcitabine increased pancreatic cancer cells' HLA-I mRNA transcripts, total protein, surface expression, and surface stability. Temperature-dependent assay results indicated that the increased HLA-I stability may be due to reduced binding of low affinity peptides. Mass spectrometry analysis confirmed changes in the HLA-I-presented peptide pool post-treatment, and computational predictions suggested improved affinity and immunogenicity of peptides displayed solely by gemcitabine-treated cells. Most of the gemcitabine-exclusive peptides were derived from unique source proteins, with a notable overrepresentation of translation-related proteins. Gemcitabine also increased expression of select immunoproteasome subunits, providing a plausible mechanism for its modulation of the HLA-I-bound peptidome. Our work supports continued investigation of immunotherapies, including peptide-based vaccines, to be used with gemcitabine as new combination treatment modalities for pancreatic cancer.

Effects of tumor-infiltrating CD8+ T cells, PD1/PD-L1 axis, and expression patterns of HLA class I on the prognosis of patients with malignant pleural mesothelioma who underwent extra-pleural pneumonectomy.

Programmed cell death protein-1 (PD1), PD1 ligand 1 (PD-L1), and human leukocyte antigen (HLA) class I molecule play pivotal roles in T cell-induced anti-tumor immunity; however, the clinical impact of these parameters in resected malignant pleural mesothelioma (MPM) cases is unknown. We immunohistochemically evaluated the tumor infiltrated lymphocytes (TILs), PD1/PD-L1 axis, and expression of HLA class I in resected specimens from 58 patients with MPM who underwent extra-pleural pneumonectomy (EPP). Higher infiltration of CD3-TIL, CD8-TIL, and PD1-TIL, loss of HLA class I, and overexpression of PD-L1 by tumor cells (PD-L1 TC) or immune cells (PD-L1 IC) were observed in 34 (58.6%), 27 (46.6%), 41 (70.7%), 45 (77.6%), 29 (50.0%), and 33 (56.4%) of 58 cases, respectively. Interestingly, the CD3-TIL score positively correlated with PD-L1 TC and PD1-TIL scores. HLA class I expression level was inversely correlated with the expression levels of PD-L1 TC and PD-L1 IC. Multivariate analysis showed that age, histology, and node metastasis were independent prognostic factors for 5-year overall survival (OS) and loss of HLA class I coincided with a positive prognosis (p = 0.011). The concomitant lack of infiltrating CD8+ T cells with no loss of HLA class I predicted worse 5-year OS (p = 0.007). Moreover, cluster classifications among multiple immunoparameters showed that categories among CD3/PD-L1 TC/HLA class I (p = 0.043), CD8/PD1/HLA class I (p = 0.032), CD8/PD-L1 TC/HLA class I (p = 0.011), and PD1/PD-L1 TC/HLA class I (p = 0.032) predicted 5-year OS in EPP cases for MPM. These immunoparameters could guide surgical indications for patients with MPM.

[Clinical significance of detecting human leukocyte antigen class I allele-lacking leukocytes in aplastic anemia].

Human leukocyte antigen (HLA) class I allele-lacking [HLA (-)] leukocytes provide compelling evidence that cytotoxic T-lymphocytes are involved in the development of aplastic anemia (AA). However, the clinical significance and precise mechanisms underlying clonal hematopoiesis by HLA (-) hematopoietic stem progenitor cells remain unknown. In HLA (-) cells from patients with AA, we discovered a common nonsense mutation at codon19 (c.19C>T, p.R7X) in exon1 (Exon1mut) of different HLA-A and HLA-B alleles. Exon1 mutation detection using droplet digital polymerase chain reaction (ddPCR) is a powerful tool for diagnosing immune pathophysiology in patients with bone marrow failure. We also looked at the prognosis of 633 patients with AA, including 127 with HLA (-) leukocytes who had been followed up for a long time. In Japanese patients with AA, HLA (-) leukocytes and concomitant aberrant clones were not associated with clonal evolution to MDS/AML. In patients with AA and both marker (-) leukocytes, HLA (-) leukocytes may indicate a lower risk of developing secondary paroxysmal nocturnal hemoglobinuria (PNH). Detecting HLA (-) leukocytes is critical for managing patients with AA and assisting physicians in selecting appropriate therapy.

Expression of human leukocyte antigen class I and ß2-microglobulin in colorectal cancer and its prognostic impact.

Downregulation of human leukocyte antigen (HLA) class I has been postulated to be a mechanism of adaptive immune escape in various tumors, especially microsatellite instability-high (MSI-H) colorectal cancer (CRC). In this study, we aimed to investigate HLA class I and ß2-microglobulin (ß2M) expression in MSI-H and microsatellite-stable (MSS) CRCs and determine its prognostic impact. The representative areas from the tumor center (TC) and tumor periphery (TP) from 300 CRCs, including 161 MSI-H and 139 MSS cases, were selected to construct a tissue microarray. Immunohistochemistry (IHC) for HLA A/B/C, ß2M, CD3, and CD8 was performed. Reduced HLA A/B/C expression was detected in 113 (70.2%) MSI-H and 54 (38.8%) MSS cases, while reduced ß2M expression was observed in 69 (42.9%) MSI-H and 17 (12.2%) MSS cases. Although reduced ß2M expression was associated with higher pathological tumor (pT) stage in MSI-H CRC with borderline significance, no association was found between HLA A/B/C and ß2M expression and survival. Interestingly, reduced HLA A/B/C expression in MSS was associated with higher stage, and reduced HLA A/B/C and ß2M expression was an independent prognostic factor in multivariate analysis. In conclusion, reduced HLA A/B/C and ß2M expression was frequently observed in immunotherapy-naive MSI-H CRC, suggesting the possibility of primary resistance to immune checkpoint inhibitor. Interestingly, downregulation of HLA A/B/C and ß2M was associated with poor prognosis in MSS cancers. Overall, IHC for HLA A/B/C and ß2M might be a feasible predictive or prognostic tool in CRC.

Prediction of treatment response from the microenvironment of tumor immunity in cervical cancer patients treated with chemoradiotherapy.

To supplement clinical decision-making in the management of cervical cancer, various prognostic factors, including tumor immune microenvironments, were examined in patients with cervical cancer treated with definitive chemoradiotherapy. We retrospectively analyzed the expression of CD8, FoxP3, HLA-1, PD-L1, and XRCC4 in 100 cases of cervical cancer. The observed tumor immune microenvironments were also classified into three types: inflamed, excluded, and cold type. Less FoxP3+ T cells and cold-type tumor were found to be poor prognostic factors in addition to non-SCC, large pre-treatment tumor volume, and three or less cycles of concurrent chemotherapy based on multivariate analysis. Cold-type tumors had significantly worse prognoses than the other two types, whereas inflamed- and excluded-type tumors showed similar 5-year disease-specific survival (P < 0.001; 0% vs. 60.3% vs. 72.3%). Radiotherapy could overcome the inhibitory immune microenvironment that occurs in excluded type. Individualized combination therapy adapted to pre-treatment tumor immunity may be necessary to improve radiotherapy outcomes in cervical cancer.

The Choice of HLA-Associated Peptide Enrichment and Purification Strategy Affects Peptide Yields and Creates a Bias in Detected Sequence Repertoire.

Understanding the most appropriate workflow for biochemical human leukocyte antigen (HLA)-associated peptide enrichment prior to ligand sequencing is essential to achieve optimal sensitivity in immunopeptidomics experiments. The use of different detergents for HLA solubilization as well as complementary workflows to separate HLA-bound peptides from HLA protein complex components after their immunoprecipitation including HPLC, C18 cartridge, and 5 kDa filter are described. It is observed that all solubilization approaches tested led to similar peptide ligand identification rates; however, a higher number of peptides are identified in samples lysed with CHAPS compared with other methods. The HPLC method is superior in terms of HLA-I peptide recovery compared with 5 kDa filter and C18 cartridge peptide purification methods. Most importantly, it is observed that both the choice of detergent and peptide purification strategy creates a significant bias for the identified peptide sequences, and that allele-specific peptide repertoires are affected depending on the workflow of choice. The results highlight the importance of employing a suitable strategy for HLA peptide enrichment and that the obtained peptide repertoires do not necessarily reflect the true distributions of peptide sequences in the sample.

Association between radiotherapy-induced alteration of programmed death ligand 1 and survival in patients with uterine cervical cancer undergoing preoperative radiotherapy.

PURPOSE: To evaluate radiotherapy-induced changes in the expression of programmed death ligand 1 (PD-L1), programmed death 1 (PD-1), and human leukocyte antigen class I (HLA-1) in patients with uterine cervical cancer, as well as infiltration of CD8+ and Forkhead box P3+ (FoxP3+) T lymphocytes into tumor tissue and the prognostic value of these parameters. MATERIALS AND METHODS: We performed immunohistochemical analysis of pre-radiotherapy biopsies and corresponding post-radiotherapy resected tissues in 104 uterine cervical cancer patients undergoing preoperative chemoradiotherapy or radiotherapy alone. We scored the expression of various proteins to distinguish positive from negative samples. RESULTS: PD-L1-expressing tumor cells (PD-L1 TC) increased significantly after chemoradiotherapy (p = 0.043). CD8+ T cell infiltration (p = 0.002) and FoxP3+ T cell infiltration (p = 0.003) decreased significantly after chemoradiotherapy. Expression of PD­1, PD-L1-expressing immune cells (PD-L1 IC), and HLA­1 did not change after chemoradiotherapy. In biopsy specimens obtained before chemoradiotherapy or radiotherapy, greater infiltration of CD8+ T cells (p = 0.001) and FoxP3+ T cells (p = 0.003) were significant predictors of better overall survival (OS). In surgical specimens obtained after chemoradiotherapy or radiotherapy, greater infiltration of PD-L1 TC was the only significant predictor of better OS (p < 0.001) and was related to a significantly lower probability of out-of-field recurrence (p = 0.005). CONCLUSION: Chemoradiotherapy induced an immunologic shift that increased PD-L1 TC. Chemoradiotherapy has immunological effects that can influence the results of treatment for uterine cervical cancer.

Human Leukocyte Antigen Class I Antibodies and Response to Platelet Transfusion in Patients Undergoing Liver Transplantation.

BACKGROUND: Patients undergoing liver transplantation (LT) frequently receive platelet transfusion (PLT) to minimize their risk of hemorrhage. Alloimmunization to platelets may lead to refractoriness to PLT. Data on the implications of platelet alloimmunization in patients undergoing LT remain limited. We examined the effect of human leukocyte antigen class I (HLA-I) antibodies on PLT refractoriness and short-term outcomes after LT. METHODS: Peritransplant clinical and PLT factors were reviewed for all adult liver or simultaneous liver-kidney transplantations from 2012 to 2017. Sensitized patients (SE) with pretransplant HLA-I calculated panel-reactive antibody ≥20% were compared with unsensitized patients (US) with calculated panel-reactive antibody <20%. The mean follow-up was 21.4 mo. RESULTS: Alloimmunization was observed in 39% of the study cohort. SE (n = 28) received 272 PLTs, and US (n = 44) received 246 PLTs. History of pregnancy was higher among SE than US (P < 0.01); otherwise, both groups had similar clinical characteristics. SE had higher rates of PLT refractoriness (66% versus 47%; P < 0.01) than US. The mean platelet corrected count increment was lower among SE compared with US up to 100 min after PLT (P < 0.05). Alloimmunization and simultaneous liver-kidney transplantation independently predicted refractoriness on multivariate logistic regression (P < 0.05). Early allograft rejection and patient survival rates were comparable for both groups. CONCLUSIONS: LT patients experienced high rates of HLA-I alloimmunization and PLT refractoriness. SE had higher rates of refractoriness and lower mean corrected count increment after transfusion compared with US. Our study suggests that further research to evaluate the utility of HLA-matched PLTs in HLA-I alloimmunized LT patients is warranted.

Association between cancer immunity and treatment results in uterine cervical cancer patients treated with radiotherapy.

OBJECTIVE: To evaluate proteins related to tumor immune response and treatment outcome from radiotherapy for uterine cervical cancer patients. METHODS: We performed a retrospective immunohistochemical staining of 81 patients with uterine cervical cancer who underwent definitive radiotherapy. We examined the expression of programmed death ligand 1, human leukocyte antigen class I, tumor-infiltrating CD8+, and forkhead box P3+ (FoxP3+) T cells in tumor tissues. RESULTS: In biopsy specimen, patients with a higher number of CD8+ T cells and FoxP3+ T cells had a better disease-specific survival than patients with a lower number of CD8+ T cells and FoxP3+ cells (P = 0.018 and P = 0.009). Multivariate analysis showed that equivalent dose in 2 Gy fractions (EQD2) of the minimum dose to 90% of the high-risk clinical target volume, FoxP3+ T cells and expression of human leukocyte antigen class I were significant prognostic factors. When the EQD2 is 70 Gy or more, a higher local control rate is obtained regardless of the number of CD8- or FoxP3-positive cells. When EQD2 is <70 Gy, the number of CD8-positive cells has a significant impact on treatment outcome: the recurrence rate (local recurrence rate + distant metastasis rate) was 46.2% in the group with a CD8 value of 230 or higher, whereas the recurrence rate was 75.7% in the group with a CD8 value of less than 230. CONCLUSION: The combination of CD8 or FoxP3 with EQD2 can be potentially useful to predict the treatment results of radiotherapy for cervical cancer, leading to individualized optimal selection of treatment for cervical cancer.

HLA Class I Downregulation by HIV-1 Variants from Subtype C Transmission Pairs.

HIV-1 downregulates human leukocyte antigen A (HLA-A) and HLA-B from the surface of infected cells primarily to evade CD8 T cell recognition. HLA-C was thought to remain on the cell surface and bind inhibitory killer immunoglobulin-like receptors, preventing natural killer (NK) cell-mediated suppression. However, a recent study found HIV-1 primary viruses have the capacity to downregulate HLA-C. The goal of this study was to assess the heterogeneity of HLA-A, HLA-B, and HLA-C downregulation among full-length primary viruses from six chronically infected and six newly infected individuals from transmission pairs and to determine whether transmitted/founder variants exhibit common HLA class I downregulation characteristics. We measured HLA-A, HLA-B, HLA-C, and total HLA class I downregulation by flow cytometry of primary CD4 T cells infected with 40 infectious molecular clones. Primary viruses mediated a range of HLA class I downregulation capacities (1.3- to 6.1-fold) which could differ significantly between transmission pairs. Downregulation of HLA-C surface expression on infected cells correlated with susceptibility to in vitro NK cell suppression of virus release. Despite this, transmitted/founder variants did not share a downregulation signature and instead were more similar to the quasispecies of matched donor partners. These data indicate that a range of viral abilities to downregulate HLA-A, HLA-B, and HLA-C exist within and between individuals that can have functional consequences on immune recognition.IMPORTANCE Subtype C HIV-1 is the predominant subtype involved in heterosexual transmission in sub-Saharan Africa. Authentic subtype C viruses that contain natural sequence variations throughout the genome often are not used in experimental systems due to technical constraints and sample availability. In this study, authentic full-length subtype C viruses, including transmitted/founder viruses, were examined for the ability to disrupt surface expression of HLA class I molecules, which are central to both adaptive and innate immune responses to viral infections. We found that the HLA class I downregulation capacity of primary viruses varied, and HLA-C downregulation capacity impacted viral suppression by natural killer cells. Transmitted viruses were not distinct in the capacity for HLA class I downregulation or natural killer cell evasion. These results enrich our understanding of the phenotypic variation existing among natural HIV-1 viruses and how that might impact the ability of the immune system to recognize infected cells in acute and chronic infection.

The Antitumor Activity of TCR-Mimic Antibody-Drug Conjugates (TCRm-ADCs) Targeting the Intracellular Wilms Tumor 1 (WT1) Oncoprotein.

Wilms tumor 1 (WT1) oncoprotein is an intracellular oncogenic transcription factor which is barely expressed in normal adult tissues but over expressed in a variety of leukemias and solid cancers. WT1-derived HLA-A*02:01 T cell epitope, RMFPNAPYL (RMF), is a validated target for T cell-based immunotherapy. We generated two T cell receptor mimic antibody-drug conjugates (TCRm-ADCs), ESK-MMAE, and Q2L-MMAE, against WT1 RMF/HLA-A*02:01 complex with distinct affinities, which mediate specific antitumor activity. Although ESK-MMAE showed higher tumor growth inhibition ratio in vivo, the efficacy of them was not so promising, which might be due to low expression of peptide/HLA targets. Therefore, we explored a bispecific TCRm-ADC that exerted more potent tumor cytotoxicity compared with TCRm-ADCs. Hence, our findings validate the feasibility of the presenting intracellular peptides as the targets of ADCs, which broadens the antigen selection range of antibody-based drugs and provides new strategies for precision medicine in tumor therapy.

HLA class I expression predicts prognosis and therapeutic benefits from tyrosine kinase inhibitors in metastatic renal-cell carcinoma patients.

PURPOSE: Classical HLA class I antigen is highly involved in antigen presentation and adaptive immune response against tumor. In this study, we explored its predictive value for treatment response and survival in metastatic renal-cell carcinoma (mRCC) patients. EXPERIMENTAL DESIGN: A TKI cohort of 111 mRCC patients treated with sunitinib or sorafenib and a non-TKI cohort of 160 mRCC patients treated with interleukin-2 or interferon-α-based immunotherapy at a single institution were retrospectively enrolled. HLA class I expression and cytotoxic T lymphocyte (CTL) density was assessed by immunohistochemistry on tissue microarrays. Association between HLA class I and CTL was also assessed in the TCGA KIRC cohort. RESULTS: In the TKI cohort, down-regulated HLA class I was associated with lower objective response rate of TKI therapy (P = 0.004), shorter overall survival (OS) (P = 0.001), and shorter progression free survival (PFS) (P < 0.001). Multivariate Cox regression model defined HLA expression as an independent prognostic factor for both OS [hazard ratio 1.687 (95% CI 1.045-2.724), P = 0.032] and PFS [hazard ratio 2.139 (95% CI 1.376-3.326), P = 0.001]. In the non-TKI cohort, HLA class I was not significantly associated with survival. HLA class I expression was associated with CTL infiltration and function, and its prognostic value was more predominant in CTL high-density tumors (P < 0.001) rather than CTL low-density tumors (P = 0.294). CONCLUSIONS: Classical HLA class I expression can serve as a potential predictive biomarker for TKI therapy in mRCC patients. Its predictive value was restricted in CTL high-density tumors. However, further external validations and functional investigations are still required.

Circulating and renal expression of HLA-G prevented chronic renal allograft dysfunction in Japanese recipients.

BACKGROUND: Although the risk of acute rejection has been studied in renal transplanted patients, there is little data about the long-term renal survival effects of non-classical human leukocyte antigen class I (HLA-G) in Japanese patients. METHOD: We investigated the changes in the estimated glomerular filtration rate (eGFR) for Japanese, and factors affecting the eGFR in 141 adult Japanese subjects whose allografts had survived for at least 1 year. Clinical background data, gender, HLA matching status, the total ischemic time, ABO incompatibility, immunosuppressive therapy, and the serum soluble(s) HLA-G5 level were examined. In addition, renal biopsy specimens from 32 cases, which were obtained before, or 2-4 weeks or one year after the transplant were also evaluated for HLA-G1/5 expression using monoclonal anti-HLA-G antibodies (clone 87G or 4H84). RESULTS: The rates of change per year in the median eGFR (ΔeGFR) and sHLA-G5 were -1.5 ml/min/1.73 m2/year and 11.8 ng/ml, respectively. A positive correlation was detected between the ΔeGFR and sHLA-G5 (r = 0.188, p = 0.025). In multivariate regression analysis, sHLA-G5 and HLA-matching were significant predictors of an improvement in eGFR (beta for sHLA-G: 0.374, p = 0.009; beta for mismatching: -1.135, p = 0.045). The renal tubular epithelial cells (TEC) in 11 cases showed a perinuclear HLA-G1/5 expression after renal transplantation. The renal HLA-G1/5-positive patients displayed much better ΔeGFR (p < 0.05). In conclusion, the sHLA-G5 level and HLA matching status are independent predictors of renal allograft function, as determined by the ΔeGFR, in Japanese patients. HLA-G1/5 was also detected on TEC in the patients with favorable renal function.

Expanding the detectable HLA peptide repertoire using electron-transfer/higher-energy collision dissociation (EThcD).

The identification of peptides presented by human leukocyte antigen (HLA) class I is tremendously important for the understanding of antigen presentation mechanisms under healthy or diseased conditions. Currently, mass spectrometry-based methods represent the best methodology for the identification of HLA class I-associated peptides. However, the HLA class I peptide repertoire remains largely unexplored because the variable nature of endogenous peptides represents difficulties in conventional peptide fragmentation technology. Here, we substantially enhanced (about threefold) the identification success rate of peptides presented by HLA class I using combined electron-transfer/higher-energy collision dissociation (EThcD), reporting over 12,000 high-confident (false discovery rate <1%) peptides from a single human B-cell line. The direct importance of such an unprecedented large dataset is highlighted by the discovery of unique features in antigen presentation. The observation that a substantial part of proteins is sampled across different HLA alleles, and the common occurrence of HLA class I nested sets, suggest that the constraints of HLA class I to comprehensively present the health states of cells are not as tight as previously thought. Our dataset contains a substantial set of peptides bearing a variety of posttranslational modifications presented with marked allele-specific differences. We propose that EThcD should become the method of choice in analyzing HLA class I-presented peptides.

Beyond Human Leukocyte Antigen Class I Antigens: Hereditary Hemochromatosis Gene Mutations in Recurrent Aphthous Oral Ulcers and Behçet Disease in the South of Tunisia.

OBJECTIVE: The aim of this work was to establish human leukocyte antigen (HLA) class I and hereditary hemochromatosis gene (HFE) mutation associations with recurrent aphthous oral ulcers (RAOU) and Behçet disease (BD) in a cohort of Southern Tunisian patients. SUBJECTS AND METHODS: A total of 232 patients with RAOU and 123 healthy controls (HCs) were enrolled in this study. The patients were divided into 2 groups based on the presence (BD+: n = 62) or absence of BD (BD-, n = 170). In the BD+ group, 28 patients had severe manifestations of BD. In the BD- group, RAOU was isolated in 81 patients, associated with mucocutaneous manifestations in 58 and with joint symptoms in 25. Complement-dependent microlymphocytotoxicity assay and polymerase chain reaction-restriction fragment length polymorphism were used to study HLA class I polymorphism and HFE mutations, respectively. RESULTS: HLA-B51 was positively associated with BD, particularly in those with severe manifestations. No association was detected with HLA class I polymorphism among the BD group. Based on stratification to clinical manifestations, the isolated RAOU was negatively associated with HLA-A1 with a difference close to significance (12 [14.81%] vs. 32 [26.02%] in HCs; p = 0.06). Furthermore, patients with mucocutaneous features had a higher frequency of HLA-B51 (14, 24.14%) than patients without mucocutaneous involvement (11, 11.37%). Considering HFE mutations, patients with isolated RAOU had a higher frequency of H63D when compared with other subgroups, especially after limiting the comparison to 27 patients of at least 5 years of follow-up. CONCLUSION: This study showed that, unlike BD, RAOU were not associated with HLA-B51. Moreover, we suggest that H63D mutation was positively associated with isolated RAOU.

Naturally processed non-canonical HLA-A*02:01 presented peptides.

Human leukocyte antigen (HLA) class I molecules generally present peptides (p) of 8 to 11 amino acids (aa) in length. Although an increasing number of examples with lengthy (>11 aa) peptides, presented mostly by HLA-B alleles, have been reported. Here we characterize HLA-A*02:01 restricted, in addition to the HLA-B*0702 and HLA-B*4402 restricted, lengthy peptides (>11 aa) arising from the B-cell ligandome. We analyzed a number of 15-mer peptides presented by HLA-A*02:01, and confirmed pHLA-I formation by HLA folding and thermal stability assays. Surprisingly the binding affinity and stability of the 15-mer epitopes in complex with HLA-A*02:01 were comparable with the values observed for canonical length (8 to 11 aa) HLA-A*02:01-restricted peptides. We solved the structures of two 15-mer epitopes in complex with HLA-A*02:01, within which the peptides adopted distinct super-bulged conformations. Moreover, we demonstrate that T-cells can recognize the 15-mer peptides in the context of HLA-A*02:01, indicating that these 15-mer peptides represent immunogenic ligands. Collectively, our data expand our understanding of longer epitopes in the context of HLA-I, highlighting that they are not limited to the HLA-B family, but can bind the ubiquitous HLA-A*02:01 molecule, and play an important role in T-cell immunity.

A new HLA-B allele, B*18:105, identified in a Caucasian Spanish individual.

HLA-B*18:105 shows two nucleotide differences regarding B*18:22 (97 AGC>AGG, 99 TAC>TAT) and B*18:52 (94 ACC>ATC, 95 CTC>ATC).

A new HLA-B allele, B*49:34, sequenced in a Spanish individual.

HLA-B*49:34 shows one nucleotide difference regarding B*49:01:01 at codon 66 (ATC>GTC, I66>V66).

MHC class I signaling: new functional perspectives for an old molecule.

Donor-specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody-mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody-mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.

Genetic risk for co-occurrence of type 1 diabetes and celiac disease is modified by HLA-C and killer immunoglobulin-like receptors.

The prevalence of celiac disease (CD) in patients with type 1 diabetes (T1D) has been reported to be 5-7 times higher than in the general population. Risk factors for co-occurrence of both diseases have not been entirely established. The aim of our study was to analyze possible impact of human leukocyte antigen (HLA) class I and killer cell immunoglobulin-like receptors (KIRs) on the co-occurrence of T1D and CD. We analyzed 67 patients with T1D, 68 patients with CD, 69 patients with both diseases (T1D+CD) and 130 controls. Statistical analysis was based on two tailed Fisher exact test with corrections for multiple testing. After stratification by DR3-DQ2, an association of HLA class I part of the COX haplotype (A1-B8-Cw7-DR3-DQ2) was not observed with each of the studied diseases separately, but it could be shown in case of the co-occurrence of T1D and CD. Only in the group of patients with coexisting diseases, the presence of HLA-C*07 (P = 8.65×10(-3) ) and HLA-B*08 (P = 0.03) but not HLA-A*01 increased the succeptibility. Our current data indicated that C*07, contributing C1 ligand (Pc = 3.67×10(-5) ) rather than B*08, that possesses no KIR ligand, could have an impact on the innate immunity rout of this susceptibility. The significant combination of C1-KIR2DL3 (Pc = 1.97×10(-4) ) observed in patients with coexisting diseases supports this hypotesis. Interestingly, no association was observed when C1 in combination with its stronger inhibitory receptor KIR2DL2 was investigated. Predominantly, weak inhibition in patients with coexisting T1D and CD could lead to a natural killer cell response, making them vulnerable for developing more than one autoimmune disease.