MHC class I and class II genes in Mexican patients with Chagas disease

Chagas' disease contributes significantly to cardiovascular morbidity and mortality in several Latin-American countries. Previous studies have reported the effect of the human leukocyte antigen (HLA) molecules in the immune response regulation of Trypanosoma cruzi infection, and the association of HLA antigens with heart damage. We studied the major histocompatibility complex (MHC) class I (HLA-A and HLA-B), and class II (HLA-DR) genes in a sample of 66 serologically positive individuals with and without cardiomyopathy, and in 127 healthy controls. The total group of seropositive individuals revealed increased frequencies of HLA-B39 (pc=4.3x10(-5), odds ratio [OR]=3.35) and DR4 (pc=1.8x10(-5), OR=2.91) when compared to healthy controls. Increased frequencies of HLA-A68 and HLA-B39 were found in asymptomatic individuals when compared to patients with cardiomyopathy (pc=0.014, OR=4.99 and pc=0.001, OR=4.46, respectively). Also, patients with cardiomyopathy exhibited increased frequency of HLA-B35 when compared to healthy controls (pc=0.048, OR=2.56). The HLA-DR16 frequency was increased in patients with cardiomyopathy compared with asymptomatic individuals (pc=0.05, OR=No determined) and healthy controls (pc=0.02, OR=5.0). The results suggest that MHC alleles might be associated with the development of chronic infection and with heart damage in Chagas' disease. HLA-DR4 and HLA-B39 could be associated directly with the infection by T. cruzi, whereas, HLA-DR16 could be marker of susceptibility to heart damage and HLA-A68 might confer protection to develop cardiomyopathy.     

Mapping and restriction of a dominant viral CD4+ T cell core epitope by both MHC class I and MHC class II

Virus-specific CD4(+) T cells contribute to effective virus control through a multiplicity of mechanisms including direct effector functions as well as "help" for B cell and CD8(+) T cell responses. Here, we have used the lymphocytic choriomeningitis virus (LCMV) system to assess the minimal constraints of a dominant antiviral CD4(+) T cell response. We report that the core epitope derived from the LCMV glycoprotein (GP) is 11 amino acids in length and provides optimal recognition by epitope-specific CD4(+) T cells. Surprisingly, this epitope is also recognized by LCMV-specific CD8(+) T cells and thus constitutes a unique viral determinant with dual MHC class I- and II-restriction.     

DNA content and MHC class II antigen expression in malignant melanoma: clinical course.

To assess the clinical value of two comparatively new properties (DNA content and MHC class II antigen expression (HLA-DR, DP, DQ) of melanoma cells) which have been independently reported to reflect the outlook for patients with malignant melanoma, we investigated retrospectively 50 stage I nodular melanomas in two comparably homogeneous groups of 23 and 27 patients, the course of whose disease differed at five years. Flow cytometry and immunohistology were used on paraffin wax embedded archival material for the analysis of DNA ploidy and detection of class II antigens, respectively. A close association was found between class II antigen expression, detected by monoclonal antibody CR3/43 (antimonomorphic DR, DP, DQ) present in 23 of 50 (46%) melanomas and unfavourable clinical course (p less than 0.005, by log rank test), but no such association was found for DNA ploidy. It is suggested that immunohistology for MHC class II antigen expression may help to predict the behaviour of nodular melanomas whereas the prognostic value of DNA ploidy is more limited. The finding that class II positive cells are found predominantly in melanomas with a substantially increased risk of metastases has implications both for concepts of tumour heterogeneity and host immunity.     

The MHC class I genes of zebrafish

Major histocompatibility complex (MHC) molecules play a central role in the immune response and in the recognition of non-self. Found in all jawed vertebrate species, including zebrafish and other teleosts, MHC genes are considered the most polymorphic of all genes. In this review we focus on the multi-faceted diversity of zebrafish MHC class I genes, which are classified into three sequence lineages: U, Z, and L. We examine the polygenic, polymorphic, and haplotypic diversity of the zebrafish MHC class I genes, discussing known and postulated functional differences between the different class I lineages. In addition, we provide the first comprehensive nomenclature for the L lineage genes in zebrafish, encompassing at least 15 genes, and characterize their sequence properties. Finally, we discuss how recent findings have shed new light on the remarkably diverse MHC loci of this species.     

Correlation of class I DNA Pvu II restriction HLA gene fragments with serologic alleles

Restriction enzyme site polymorphisms for Pvu II endonuclease are examined in a panel of DNAs isolated from peripheral blood lymphocytes of HLA-typed individuals. 21 polymorphic bands are detected from a total of 39 restriction fragments analyzed, only 9 of them corresponding to common variable morphs. Three polymorph fragments only correlate with known HLA-A and -B serologic alleles.     

New polymorphic microsatellite markers in the human MHC class II region

The human major histocompatibility complex (MHC) class II region spans approximately 1.1 Mb and presently contains over 30 functional genes Susceptibility loci to numerous diseases, mainly of autoimmune nature are known to map to the this region, as assessed by associations with particular HLA class II alleles. However, it has been difficult to precisely localize these susceptibility loci to a single gene, for example DQB1 or DRB1, due to the tight linkage disequilibrium observed in the HLA class II region. To facilitate disease mapping within this region, we have analyzed 2 to approximately 5 bases short tandem repeats (microsatellites) in this same region. A total of 494 microsatellites were identified from the genomic sequence of the HLA class II region. These consist of 158 di-, 65 tri-, 163 tetra-, and 108 pent-nucleotide repeats, out of which four were located within the coding sequence of expressed genes (Daxx, BING1, RXRB and COL11A2). Twenty-two repeats were selected as polymorphic markers due to their high (average) number of alleles (8.9) as well as their high polymorphic content value (PIC) (0.58). These novel polymorphic microsatellites will provide useful genetic markers in HLA-related research, such as genetic mapping of HLA class II-associated diseases, transplantation matching, population genetics, identification of recombination hot spots as well as linkage disequilibrium studies.     

New polymorphic microsatellite markers in the human MHC class I region

The human major histocompatibility complex (MHC) class I region is believed to contain a large number of genes encoding susceptible factors for diseases such as Behcet's disease, Graves disease and psoriasis vulgaris. To identify the causative genes of those diseases, we have conducted large-scale genomic sequencing and determined the 1.8 Mb entire HLA class I region from the MICB gene to the HLA-F gene. During the course of genomic sequencing, a total of 731 microsatellite sequences with dinucleotide to pentanucleotide repeats were found in this region. Previously, we reported that 26 microsatellites between MICB and S on the most centromeric side of the class I region, and between HSR1 and HLA-92/L in the midst of the class I region were highly polymorphic, and served as excellent genetic markers. In this paper, in order to fill the gaps with no known polymorphic microsatellites available in the HLA class I region, 12 new polymorphic microsatellite markers were recruited from the 1.8 Mb region including the remaining class I segments, namely between S and HSR1, and between HLA-92/L and HLA-F The average number of alleles at these new microsatellite loci was 8.2 with a polymorphism content value (PIC) of 0.63. These 38 markers in total almost uniformly interspersed in the HLA class I region will enable us to search precisely for the location of disease susceptible loci within the HLA class I region by association and for linkage analyses.     

MHC class II antigen presentation and immunological abnormalities due to deficiency of MHC class II and its associated genes

Antigen presentation by Major Histocompatibility Complex (MHC) class II molecules plays an important role in controlling immunity and autoimmunity. Multiple co-factors including the invariant chain (Ii), HLA-DM and HLA-DO are involved in this process. While the role for Ii and DM has been well defined, the biological function of DO remains obscure. Our data indicate that DO inhibits presentation of endogenous self-antigens and that developmentally-regulated DO expression enables antigen presenting cells to preferentially present different sources of peptide antigens at different stages of development. Disruption of this regulatory mechanism can result in not only immunodeficiency but also autoimmunity. Despite the fact that deletion of each of the three genes in experimental animals is associated with profound immunological abnormalities, no corresponding human diseases have been reported. This discrepancy suggests the possibility that primary immunodeficiencies due to a genetic defect of Ii, DM and DO in humans are under diagnosed or diagnosed as “common variable immunodeficiency”, a category of immunodeficiency of heterogeneous or undefined etiology. Clinical tests for any of these potential genetic defects are not yet available. We propose the use of multi-color flow cytometry in conjunction with intracellular staining to detect expression of Ii, DM, DO in peripheral blood B cells as a convenient reliable screening test to identify individuals with defects in antigen presentation.     

Immunohistological evaluation of MHC class I and II antigen expression on nevi and melanoma: relation to biology of melanoma

MHC antigen expression on 20 nevi, and 35 primary and 95 metastatic melanomas was studied by immunoperoxidase techniques using monoclonal antibodies to identify the antigens on frozen tissue sections. DR antigens were not detected on nevi but were detected on 71% of primary melanomas and 56% of metastases, suggesting that this antigen may be a useful marker of malignant transformation of nevi. Expression of class II antigen could not be related to other prognostic histological features of primary melanoma such as tumour thickness, but comparison of the common phenotypes of primary and metastatic melanoma suggested that expression of DR antigens alone in the absence of DP, DQ and ABC antigens may be an indicator of metastatic potential. Class I (HLA-A,B,C) antigens were also expressed infrequently on nevi but were detected on 43% of primary melanomas and 34% of metastases. HLA-A,B,C expression was inversely related to thickness of the primary melanoma. This as well as the lower expression of class I antigens on metastases, may indicate that growth and spread of melanoma may be inhibited by MHC (class I) dependent cytotoxic T cell responses. Expression of class I MHC antigens was unrelated to class II antigens. Expression of DR was more common than DP or DQ, but the latter with one exception, were not expressed in the absence of DR antigens. Significant differences were not found in MHC antigen expression on metastases in lymph nodes compared to those in subcutaneous sites, but further studies are needed to determine whether such differences may exist between metastases in other visceral sites.     

Expression of MHC class I and class II antigens in pancreatic adenocarcinomas

The antigens encoded by the major histocompatibility complex (MHC) are cell surface glycoproteins that play a fundamental role in the regulation of the immune response. Anomalous MHC expression in tumor cells has been viewed as an important feature to escape tumor recognition by immune cells. Low or absent MHC class I expression as well as ectopic MHC class II expression have been often observed to correlate with high grade malignancy and metastatic potential in a variety of human cancers. To date, very little investigation of MHC (HLA in man) class I and class II expression inhuman pancreatic cancer has been reported. We investigated this aspect on frozen sections of 8 pancreatic adenocarcinomas and 18 established in vitro cell lines. HLA class I was expressed in all but two cancers whereas de novo HLA class II expression was detected in 3 of 8 cancers. Interestingly, a hierarchy in the expression of the various subsets of HLA class II was found with HLA-DR>-DP>-DQ. Results on cell lines strongly resembled the ones obtained in cancer tissues. However, a peculiar feature was observed in certain cell lines. HLA class II antigens were expressed in only a few cell lines and in some of them a mixed population of positive and negative cells was found. Sorting and cloning of the two populations confirmed the existence of tumor cell clones with stable and distinct HLA class II phenotype. Taken together, these results indicate the cellular heterogeneity of pancreatic cancer cells with regard to the qualitative and quantitative expression of major histocompatibility complex genes, and may provide new insights for a better understanding of the tumor-host relationships in this extremely severe form of neoplasia.     

Expression of MHC class I and class II antigens in colonic carcinomas

Malignant and non-malignant ('normal') colonic tissues from patients with colonic carcinoma were examined for the expression of MHC class I and class II antigens by immunoenzymatic staining using monoclonal antibodies. The amount of class I antigen as detected by 2 monoclonal antibodies, FMC 16 or W6/32 was clearly diminished in 11 of 14 tumours when compared to the amount present on 'normal' colonic tissue from the same individual. The loss of class I antigen did not correlate with tumour stage or differentiation. The reactivities of FMC 16 and W6/32 with these tissues were not identical, which indicates that the 2 monoclonal antibodies may recognize different epitopes on the HLA class I molecule. Class II antigens were absent from 'normal' colonic epithelium but were present on 20 of 28 tumours, with DR being detected more often than DP, and DQ found only on 4 of 28 tumours. When present, staining for class II antigens was heterogeneous within the tumour, in that all tumour cells did not stain equally. DR and DP antigens were found more often on moderately or poorly differentiated adenocarcinomas and on stage B, C and D tumours in that order of frequency. Thus tumours with a better prognosis were less likely to express DR and DP. The expression of DQ was unrelated to staging or differentiation.     

Heterogeneity of class I and class II MHC sequences in Schistosoma mansoni

We investigated the genetic variations in class I and class II major histocompatibility complex (MHC) genes of Schistosoma mansoni and the effects of host MHC genotypes. S. mansoni was maintained in combinations of two mouse strains with different MHC genotypes, and the MHC gene sequences of the cercariae were investigated. The detected class I MHC gene sequences were variable, with high similarity between the H-2D^b murine host and the parasite. For other combinations, however, the parasite sequence was homologous to those of anthropoids. All class II MHC sequences detected in S. mansoni were homologous to those of anthropoids. Our results suggest that the genetic variation in the MHC sequences of S. mansoni is derived in part from the current host, indicating horizontal transfer of the sequences from mammal to parasite.