HLA class I and class II antigens associated with multiple myeloma in southern Africa

While the exact aetiology of myeloma is unknown, genetic factors feature among the potential risk factors. The HLA phenotypes in African blacks with myeloma (the commonest haematopoietic malignancy in this group) have not been characterized. The purpose of this study was to determine the HLA class I and class II phenotypes of patients with multiple myeloma and to compare the findings to an ethnically matched control group of 100 individuals. Analysis of the HLA class I and class II phenotypes in 62 myeloma patients revealed: (i) a corresponding statistically significant association with HLA B18 [odds ratio (OR) 6.3; 95% confidence interval (CI) 1.013-39.727; P < 0.005]; (ii) no statistically significant association with HLA B13, Cw2, Cw6 or the DR and DQ antigens; and (iii) a statistically significant negative (protective) association with HLA Cw7 (OR 0.4; 95% CI 0.21-0.87; P < 0.005). This study suggests that although genetic factors may play a role in the multifactorial aetiology of multiple myeloma, with the exception of HLA B18, there is no specific association between HLA types and multiple myeloma in South African blacks.     

Mechanisms of endogenous MHC class II presentation by tumor cells

Evaluation of: Tsuji T, Matsuzaki J, Caballero OL et al. Heat shock protein 90-mediated peptide-selective presentation of cytosolic tumor antigen for direct recognition of tumors by CD4(+) T cells. J. Immunol. 188, 3851-3858 (2012). In this study, Tsuji and colleagues investigated how tumor antigen NY-ESO-1 was processed by melanoma cells and subsequently presented on HLA class II for the recognition of NY-ESO-1-specific CD4(+) T cells. Using a combination of specific inhibitors and RNAi techniques, they found that tumor cells utilize a novel peptide selective antigen presentation pathway that requires both proteasome and endosomal protease-dependent processing, as well as heat-shock protein 90-dependent chaperoning. This newly described tumor-specific, endogenous MHC class II antigen presentation could have an impact on both antitumor or protumor T-cell responses.     

Reversal of tolerance to human MUC1 antigen in MUC1 transgenic mice immunized with fusions of dendritic and carcinoma cells

Immunological unresponsiveness established by the elimination or anergy of self-reactive lymphocyte clones is of importance to immunization against tumor-associated antigens. In this study, we have investigated induction of immunity against the human MUC1 carcinoma-associated antigen in MUC1 transgenic mice unresponsive to MUC1 antigen. Immunization of adult MUC1 transgenic mice with irradiated MUC1-positive tumor cells was unsuccessful in reversing unresponsiveness to MUC1. By contrast, fusions of dendritic cells with MUC1-positive tumor cells induced cellular and humoral immunity against MUC1. Immunization with the dendritic cell fusions that express MUC1 resulted in the rejection of established metastases and no apparent autoimmunity against normal tissues. These findings demonstrate that unresponsiveness to the MUC1 tumor-associated antigen is reversible by immunization with heterokaryons of dendritic cells and MUC1-positive carcinoma cells.     

HLA class I and II polymorphisms in Mexican Mestizo patients with dengue fever

Host genetics in dengue hemorrhagic fever (DHF) pathophysiology has not been extensively investigated. Most studies have focused on HLA in different populations; however these reported associations have not been replicated. We performed a case-control study to analyze possible associations of HLA-A, HLA-B, HLA-Cw, HLA-DRB1 and HLA-DQB1 alleles with clinical disease severity caused by dengue virus infection. Our population consisted of 39 individuals (DF: 23, DHF: 16) and 34 healthy controls from the State of Morelos, Mexico. HLA loci were genotyped by nucleotide sequencing method. Statistical analyses revealed associations in three alleles: HLA-B*35 was negatively associated with symptomatic disease (p < 1 × 10⁻⁴, p_c = 0.01, OR = 0.12, 95%CI = 0.037-0.39), and DF (p = 0.0007, p_c = 0.03, OR = 0.13, 95%CI = 0.031-0.51). HLA-DQB1*0302 was positively associated with DHF (p = 0.018, p_c = NS, OR = 5.02, 95%CI = 1.05-25.34), and negatively with DF (p = 0.011, p_c = NS, OR = 0.23, 95%CI = 0.06-0.84). HLA-DQB1*0202 was positively associated with DF only (p = 0.012, p_c = NS, OR = 7.0, 95%CI = 1.11-73.8). We identified possible associations of HLA-B and HLA-DQB1 alleles with the risk of developing symptomatic disease, DF and DHF in a Mexican Mestizo population.     

T84-intestinal epithelial exosomes bear MHC class II/peptide complexes potentiating antigen presentation by dendritic cells

BACKGROUND & AIMS: Intestinal epithelial cells release antigen-presenting vesicles (exosomes) bearing major histocompatibility complex class II/peptide complexes stimulating specific immune responses in vivo. To characterize further the role of human epithelial exosomes in antigen presentation, their capacity to load antigenic peptides, bind immune target cells, and induce T-cell activation was analyzed in vitro. METHODS: The capacity of exosomes derived from the HLA-DR4-expressing, intestinal epithelial cell line T84 to load the HLA-DR4-specific peptide (3)H-HSA 64-76 and to activate a HLA-DR4-restricted T-cell hybridoma was tested in the presence or absence of human monocyte-derived dendritic cells (DCs). Interaction of fluorescein isothiocyanate-labeled exosomes with T cells and DCs was analyzed by flow cytometry and confocal microscopy. RESULTS: T84-derived exosomes, enriched in CD9, CD81, CD82, and A33 antigen, were capable of binding specifically human serum albumin (HSA) 64-76 peptide on HLA-DR4 molecules and of interacting preferentially with DCs. HSA-loaded exosomes were unable to activate the T-cell hybridoma directly but induced a productive T-cell activation through DCs. When HSA peptide was bound to exosomal HLA-DR4 molecules instead of in a soluble form, the threshold of peptide presentation by DCs was markedly decreased (x10(-3)). CONCLUSIONS: Exosomes released by intestinal epithelial cells bear exogenous peptides complexed to major histocompatibility complex class II molecules and interact preferentially with DCs, strongly potentiating peptide presentation to T cells. Epithelial exosomes constitute a powerful link between luminal antigens and local immune cells by mediating the transfer of tiny amounts of luminal antigenic information and facilitating immune surveillance at mucosal surfaces.     

HLA class II-restricted antigen presentation of endogenous bcr-abl fusion protein by chronic myelogenous leukemia-derived dendritic cells to CD4(+) T lymphocytes

Bcr-abl fusion peptide-specific CD4+ T-lymphocyte clones have recently been shown to augment colony formation by chronic myelogenous leukemia (CML) cells in a bcr-abl type-specific and HLA class II-restricted manner without addition of exogenous antigen. These findings suggest that CML cells can naturally process and present endogenous bcr-abl fusion protein to CD4+ T lymphocytes in the context of HLA class II molecules. To verify this possibility, the ability of CML-derived dendritic cells (DCs) to present endogenous bcr-abl fusion protein to bcr-abl fusion peptide-specific CD4+ T-lymphocyte clones was investigated. The bcr-abl b3a2 peptide-specific and HLA-DRB1*0901-restricted CD4+ T-lymphocyte clones produced interferon-gamma in response to stimulation with monocyte-derived DCs from HLA-DRB1*0901+ patients with b3a2 type CML. In contrast, DCs from patients with HLA-DRB1*0901- or b2a2 type CML and those from healthy individuals did not exert stimulatory activity on bcr-abl-specific CD4+ T-lymphocyte clones. The response of CD4+ T-lymphocyte clones to CML-derived mature DCs was higher than that to immature DCs and was inhibited by anti-HLA-DR monoclonal antibody. These data suggest that CML-derived DCs can process and present endogenous bcr-abl fusion protein to CD4+ T lymphocytes.     

Molecular typing of HLA class I and class II antigens in Indian kala-azar patients

HLA has been shown to be associated with many diseases. To find out whether host genetic factors like the HLA are involved in susceptibility to kala‐azar (visceral leishmaniasis) in India, we formulated an association study with genetically related controls. All samples were typed by PCR SSOP (sequence specific oligonucleotide probes) for HLA class I (A and B) and class II (DR) antigens. The test of association we used was the transmission disequilibrium test (TDT). No significant evidence for association with any of the three HLA loci was obtained.     

Autophagy mediates transporter associated with antigen processing-independent presentation of viral epitopes through MHC class I pathway

The endogenous presentation of the majority of viral epitopes through MHC class I pathway is strictly dependent on the transporter associated with antigen processing (TAP) complex, which transfers the peptide products of proteasomal degradation into the endoplasmic reticulum. A small number of epitopes can be presented through the TAP-independent pathway, the precise mechanism for which remains largely unresolved. Here we show that TAP-independent presentation can be mediated by autophagy and that this process uses the vacuolar pathway and not the conventional secretory pathway. After macroautophagy, the antigen is processed through a proteasome-independent pathway, and the peptide epitopes are loaded within the autophagolysosomal compartment in a process facilitated by the relative acid stability of the peptide-MHC interaction. Despite bypassing much of the conventional MHC class I pathway, the autophagy-mediated pathway generates the same epitope as that generated through the conventional pathway and thus may have a role in circumventing viral immune evasion strategies that primarily target the conventional pathway.     

HistoCheck: rating of HLA class I and II mismatches by an internet-based software tool

HLA polymorphism is a major barrier for hematopoietic stem cell and solid organ transplantation. To estimate the allogeneic potential between HLA-mismatched stem cell donor/recipient pairs, we recently proposed a matching score (dissimilarity index) that is based on the structural data of HLA class I molecules, and on the functional similarity of amino acids (AA). This first approach revealed new features about presumptive subtype allogenicities within the HLA-A*23 and A*24 groups. We have now developed an internet-based software tool ("HistoCheck") that is capable to assess the allogenicity (matching score) between any pair of clinically relevant HLA class I, and also class II, alleles. Newly described HLA sequences will be regularly integrated into the database according to the nomenclature for factors of the HLA system updates. The software is intended to be a first step for estimating the allogenicity of HLA mismatches in peculiar clinical settings, as long as there are no reliable in vitro or clinical studies available. The algorithm can later be modified according to functional data, for example, peptide-binding specificities. With the extension of the sequence similarity concept to all clinically relevant HLA class I and II loci, HistoCheck may contribute to prevent HLA mismatching being a matter of chance.     

MHC class II distribution in dendritic cells and B cells is determined by ubiquitin chain length

Dendritic cells (DCs) and B cells present antigen-derived peptides bound to MHC class II (MHC II) molecules for recognition by CD4-positive T lymphocytes. DCs control the intracellular traffic of peptide-MHC II complexes by regulating the ubiquitination of MHC II. In resting or "immature" DCs, ubiquitinated MHC II molecules are targeted to lysosomes, but upon pathogen-induced "maturation," ubiquitination is down-regulated and MHC II can accumulate on the plasma membrane of mature DCs. Although B cells constitutively ubiquitinate their MHC II, it unexpectedly remains at the surface. We find that DCs and B cells differ in MHC II-conjugated ubiquitin (Ub) chain length: four to six Ub in immature DCs vs. two to three in B cells. In both cell types, experimentally increasing Ub chain length led to efficient lysosomal transport of MHC II, whereas MHC II with fewer than two Ubs did not reach lysosomes. Thus, Ub chain length plays a crucial role in regulating the intracellular fate and function of MHC II in DCs and B cells.     

Use of class I and class II HLA loci for predicting age at onset of type 1 diabetes in multiple populations

Aims/hypothesis

The study aimed to assess, in multiple populations, the role of HLA alleles on early and late age at onset of type 1 diabetes.

Methods

Stepwise linear regression models were used to determine which HLA class I and class II risk alleles to include. High-resolution genotyping data for patients from the Type 1 Diabetes Genetics Consortium (T1DGC) collection (n?=?2,278) and four independent cohorts from Denmark, Sardinia and the USA (Human Biological Data Interchange [HBDI] and Joslin Diabetes Center) (n?=?1,324) (total n?=?3,602) were used to assess the role of HLA variation on age of onset and predict early onset (age ≤5?years) and late onset (age ≥15?years) of type 1 diabetes.

Results

In addition to carriage of HLA class I alleles A*24:02, B*39:06, B*44:03 and B*18:01, HLA class II DRB1-DQB1 loci significantly contributed to age at onset, explaining 3.4% of its variance in the combined data. HLA genotypes, together with sex, were able to predict late onset in all cohorts studied, with AUC values ranging from 0.58 to 0.63. Similar AUC values (0.59–0.70) were obtained for early onset for most cohorts, except in the Sardinian study, in which none of the models tested had significant predictive power.

Conclusions/interpretation

HLA associations with age of onset are consistent across most white populations and HLA information can predict some of the risk of early and late onset of type 1 diabetes. Considerable heterogeneity was observed between Sardinian and other populations, particularly with regard to early age of onset.     

Modulation of HLA class I expression in multidrug-resistant human rhabdomyosarcoma cells

An abnormal HLA expression has been detected in some tumors including rhabdomyosarcoma (RMS). Classical cytotoxic treatment of these tumors, the most common childhood soft tissue malignancy, may induce multidrug resistance (MDR) associated with the expression of a 170-kDa membrane-associated glycoprotein (P-glycoprotein). In order to analyse the connection between modulation of HLA expression and the development of the MDR phenotype mediated by P-glycoprotein in RMS, we used three resistant RMS cell lines; two of these resistant cell lines (TE.32.7.DAC and RD-DAC) were established by in vitro exposure to actinomycin D, a drug of choice in the treatment of RMS; the resistant RMS- GR cell line was established from an embryonal RMS tumor after polychemotherapy. Our results showed that all the resistant cell lines showed a significant increase in the expression of HLA class I surface antigens in comparison to drug-sensitive cells. Blockade of P-glycoprotein with verapamil led to a decrease in HLA class I expression in RMS resistant cell lines. However, no modulation of HLA class II expression was observed in any of the three analyzed cell lines. These findings support the hypothesis that the development of resistance mediated by mdr 1/P-glycoprotein, directly influences the expression of HLA class I in RMS cells, inducing to upregulation. This effect may be relevant to the application in RMS of immunotherapy against tumor-associated antigens presented by HLA class I molecules.