Major Histocompatibility Complex Phenotype Research Articles

Trans-specific polymorphism and the convergent evolution of supertypes in major histocompatibility complex class II genes in darters (Etheostoma).

Major Histocompatibility Complex (MHC) genes are one of the most polymorphic gene groups known in vertebrates. MHC genes also exhibit allelic variants that are shared among taxa, referred to as trans‐specific polymorphism (TSP). The role that selection plays in maintaining such high diversity within species, as well as TSP, is an ongoing discussion in biology. In this study, we used deep‐sequencing techniques to characterize MHC class IIb gene diversity in three sympatric species of darters. We found at least 5 copies of the MHC gene in darters, with 126 genetic variants encoding 122 unique amino acid sequences. We identified four supertypes based on the binding properties of proteins encoded by the sequences. Although each species had a unique pool of variants, many variants were shared between species pairs and across all three species. Phylogenetic analysis showed that the variants did not group together monophyletically based on species identity or on supertype. An expanded phylogenetic analysis showed that some darter alleles grouped together with alleles from other percid fishes. Our findings show that TSP occurs in darters, which suggests that balancing selection is acting at the genotype level. Supertypes, however, are most likely evolving convergently, as evidenced by the fact that alleles do not form monophyletic groups based on supertype. Our research demonstrates that selection may be acting differently on MHC genes at the genotype and supertype levels, selecting for the maintenance of high genotypic diversity while driving the convergent evolution of similar MHC phenotypes across different species.

Cellular immune responses in hemophilia: why do inhibitors develop in some, but not all hemophiliacs?

Advances in molecular immunology over the past two decades permit a better understanding of why antibodies develop to peptide antigens like factor VIII and the events that lead to the development of these antibodies. Two important variables that are critical in antibody formation are (i) the molecular defect in FVIII and the consequences of that defect on translation and protein production, and (ii) the major histocompatibility complex (MHC) molecules which bind specific peptide sequences and present those peptides to CD4 T lymphocytes to initiate the cellular cascade leading to B-cell stimulation and differentiation, and ultimately to antibody formation. Inhibitors develop in hemophilia because transfused FVIII can be seen as a foreign protein and elicits an immune response in much the same way that any other foreign protein might elicit an immune response. However, not all hemophiliacs generate an immune response, either because they do not recognize FVIII as foreign or because their MHC phenotype is such that a cellular immune response is not initiated. In this model, it is the combination of molecular defect and MHC phenotype that determines inhibitor formation. The interplay of these two variables in the context of why some but not all hemophiliacs develop antibodies after treatment with replacement factor is reviewed.

Epigenetic silencing of the CIITA gene and posttranscriptional regulation of class II MHC genes in ocular melanoma cells.

Primary uveal melanocytes and many ocular melanoma cells are resistant to interferon (IFN)-gamma-mediated induction of major histocompatibility complex (MHC) class II molecule expression. This suppression of class II MHC induction is considered to be one of the ways in which the eye is able to inhibit inflammatory responses. However, the mechanism(s) of this suppression is unknown. In this study, we have probed the molecular basis of this phenotype and report two distinct mechanisms underlying this phenotype. Primary ocular melanocytes and ocular melanoma cell lines (retaining this IFN-gamma-resistant class II MHC phenotype) were examined for the expression of class II MHC molecules on the cell surface by flow cytometry. Class II MHC gene expression was further examined using Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR) analyses. The IFN-gamma signal-transduction pathway was found to be intact by electrophoretic mobility shift assay (EMSA) and transfection of reporter constructs. The lack of class II MHC gene expression appears to result from at least two mechanisms: (1) a specific inhibition of CIITA (class II transactivator) gene expression (reminiscent of trophoblasts), and (2) posttranscriptional regulation of class II MHC genes. The inability of primary uveal melanocytes and ocular melanoma cells to express class II MHC molecules after treatment with IFN-gamma has been found to map to two distinct points in the class II MHC biosynthetic pathway. The predominant mechanism appears to involve the silencing of the endogenous gene encoding the class II transactivator (CIITA). Here, the blockade does not involve signal transduction from the IFN-gamma receptor, but rather involves a specific silencing of the CIITA gene. A second mechanism involves the posttranscriptional regulation of class II MHC genes.

Major histocompatibility complex phenotypes influence serum testosterone concentration.

(a) To confirm our earlier observation that the phenotype HLA-DR4,7 occurs with higher frequency in male patients with rheumatoid arthritis (RA) than in female patients. (b) To test the hypothesis that DR7 is associated with low normal serum testosterone (Te) levels in healthy males; this might explain the increased frequency of DR4,7 in male patients since there appears to be a relationship between low serum Te and RA. (c) To characterize the association between HLA alleles and serum Te concentration in healthy males. An additional 82 Newfoundland (NF) RA patients were HLA-DR typed and, combined with our earlier data and data from the 11th International Histocompatibility Workshop, gave HLA-DR and sex information on 373 RA patients. Ninety-four healthy NF males were typed for HLA, the microsatellite marker TNFa (located close to the tumour necrosis factor alpha gene) and complement factor B (BF). An additional 38 males were included, selected partly based on their HLA-B type. We confirmed our earlier finding of a higher frequency of HLA-DR4,7 in male RA patients compared with female RA patients (P<0.01). Contrary to our expectations we found that DR7 was associated with higher than mean values of Te as were B5, B27, DR1, TNFa7 and BF F positivity. Conversely, low Te concentrations were found in men with B15, DR2, DR5, TNFa5 and who were BF F negative. In 28 male 'early-onset' RA patients we did not find an increased frequency of HLA alleles associated with low Te levels as compared with the frequency in 41 'late-onset' patients, suggesting that if low Te level is a risk factor and is present before onset of RA then the level cannot be explained by an association between Te level and major histocompatibility complex (MHC) phenotype. This study indicates that a man's MHC phenotype may influence his serum Te concentration, but the relationship of this, if any, to the pathogenesis of RA remains an area of speculation.

Genetic features of Mexican women predisposing to cancer of the uterine cervix

Cervical carcinoma is the most common neoplasia in Mexican women. Previous studies report association of this neoplasia with the major histocompatibility complex (MHC) antigens in Caucasians. In the present study, we compared antigen frequencies of class I and class II MHC phenotypes in patients and ethnically matched healthy controls. Patients had significantly increased frequencies of HLA-A2 ( PC = .000003) and HLA-DR5 ( PC = .01) as compared with healthy controls. Conversely, we found a significant decrease of HLA-DR6 ( PC = .01), HLA-DR2 ( PC = .0005) and HLA-DR1 ( PC = .0009) as compared with healthy controls. These results confirm some previous studies on HLA-associations with cervical carcinoma and reinforce the theory of independent mechanisms of MHC class I and class II genes in the etiopathogenesis of this disease.

Independent Associations of the HLA-B27 Antigen and the Complement Haplotype SC21 in Chronic Anterior Uveitis

There is evidence of an association between major histocompatibility complex (MHC) genes and acute anterior uveitis; here the authors report the frequency of class I and class III MHC phenotypes in 32 Mexican mestizo patients with chronic anterior uveitis and compared them to those present in 100 ethnically matched healthy controls. Results showed in patients statistically significant increased frequencies of HLA-B(27) antigen (pC=0.02, OR=6.33, 95+ CI:1.63-26.47) and the complotype SC(21) (pC=0.04, OR=4.5, 95+ CI:1.40-14.67); the authors found a decreased frequency of HLA-B(35) (p=0.006, OR=0.10, 95+ CI: 0.00-0.65) as compared to normal controls. None of the individuals bearing the SC(21) complotype were positive for HLA-B(27), suggesting independent roles of the class I and class III antigens in the genetic susceptibility to chronic anterior uveitis.

Resistance to collagen-induced arthritis in rats and rhesus monkeys after immunization with attenuated type II collagen.

Immunization of susceptible rodent or primate species with type II collagen (b-CII) from bovine origin induces type II collagen-induced arthritis (CIA). The disease is characterized as a systemic polyarthritis associated with humoral and cellular autoimmunity to CII and shares similarity with human arthritic diseases. The objective of this study was to develop a procedure for induction of resistance to CIA in animals, which possess a certain major histocompatibility complex phenotype that makes them prone to develop CIA (susceptible). It is shown that by immunization with an attenuated form of CII, in which arthritogenic epitopes have been destroyed by heat denaturation, disease resistance is induced in a susceptible inbred rat strain (RT-1u) and in an outbred population of susceptible rhesus monkeys (lacking the Mamu-A26 allele). In both species the disease resistance is connected with modulation of anti-CII autoantibodies of the IgM isotype. This protocol may provide a basis for effective and safe methods to induce protection to autoimmune arthritis in those subjects that are genetically prone to develop such a disease.

Human cytotoxic T cells stimulated by antigen on dendritic cells recognize the N, SH, F, M, 22K, and 1b proteins of respiratory syncytial virus.

We examined the human cytotoxic T-cell repertoire of nine adults to 9 of the 10 proteins of respiratory syncytial (RS) virus. Peripheral blood mononuclear cells from normal adults were stimulated with RS virus in vitro. The resulting polyclonal cultures were tested for lysis of B-lymphoblastoid cell lines infected with recombinant vaccinia viruses expressing each of nine individual RS virus proteins. The use of peripheral blood dendritic cells to present antigen gave more easily reproducible results over a shorter culture period than conventional methods. The six RS virus proteins most strongly recognized were the nucleoprotein N (nine of nine donors with greater than 10% above background lysis; P = 0.0004), the surface proteins SH (six of nine donors; P = 0.002) and F (five of nine donors; P = 0.008), the matrix proteins M (five of nine donors; P = 0.004) and 22K (three of nine donors; P = 0.01) and the nonstructural protein 1b (six of nine donors; P = 0.004). There was no significant recognition of the major surface glycoprotein G (two of nine donors), the internal phosphoprotein P (one of nine donors), or the nonstructural protein 1c (one of nine donors). Recognition was major histocompatibility complex class I restricted, but no association between major histocompatibility complex phenotype and protein specificity of T cells was seen. Recognition of F and 22K appeared to be associated with recent infection indicated by increased levels of anti-RS virus immunoglobulin G antibody in serum measured by enzyme-linked immunosorbent assay. Since cytotoxic T-cell recognition of RS virus proteins has been demonstrated to be important in the clearance of virus from infected hosts, the N, M, SH, 1b, F, and 22K proteins should be considered potential vaccine components.

Outgrowth of Stable Class I Major Histocompatibility Complex-Expressing Subsets From Immunogenic Variants of a Murine Mammary Carcinoma: Association with a Differentially Staining Region on Chromosome 9

We have examined interactions among intratumor subpopulations during the rejection of immunogenic variants of a murine mammary carcinoma (SPI) and in the outgrowth of tumorigenic "revertant" subsets. Analysis of subclones isolated during the early phase of rejection of one immunogenic variant revealed extensive cellular heterogeneity of tumor-forming ability and class I major histocompatibility complex (MHC) expression. Two main categories of subclones were identified. One set expressed high levels of class I MHC (MHCH) and grew poorly or not at all in normal syngeneic mice. The second set of clones expressed generally low levels of class I MHC (MHCL) and exhibited progressive growth in vivo, similar to the parent tumor. The steady-state mRNA levels for class I MHC and beta 2-microglobulin were constitutively elevated in MHCH clones compared to MHCL clones or the parent tumor. However, in vivo tumorigenic outgrowths from immunogenic variants always expressed the MHCH phenotype. A cytogenetic analysis was carried out to determine the clonal origin and lineage relationship of in vivo selected tumor outgrowths. Surprisingly, tumor outgrowths from mixtures of karyotypically distinct MHCH and MHCL subclones were derived from one lineage within the MHCH subset, despite the fact that MHCH subclones exhibited slower growth in vivo than MHCL subsets when analyzed individually. These results suggest that in polyclonal populations the various subsets sometimes interact in a way that overrides the influence of immunogenic and MHC phenotypes of individual subclones.

Production of alloantisera against class II bovine lymphocyte antigens (BoLA) by cross‐immunization between class I matched cattle

This paper describes the production of alloantisera directed against bovine major histocompatibility complex (MHC) (BoLA) class II antigens in animals whose MHC phenotypes had been defined by one dimensional isoelectric focusing. Animals of closely matched BoLA class I types were selected by serology and subsequently typed for class I and class II by 1D-IEF of immunoprecipitated antigens. Those with similar class I type by both methods, but differing at the class II locus, were chosen for reciprocal immunization. Cross-immunization was by two skin implantations 6 weeks apart. The resulting antisera showed low titre after the first immunization and elevated titre 3 weeks after the second immunization. The sera reacted strongly with cells expressing specific BoLA class II antigens. The pattern of reactivity correlated well with IEF class II typing on a panel of animals representing all of the class II IEF types present in the Friesian population.

Cells of Chemically Induced Tumors Differentially Express Major Histocompatibility Complex Class I Antigens

Several recent studies have indicated that alterations in expression of major histocompatibility complex (MHC) antigens by tumor cells affects the ability of the host to mount an effective antitumor immune response. To investigate whether newly induced tumors frequently exhibit altered MHC antigen expression, we used methylcholanthrene to induce a series of tumors and elevated MHC antigen expression by these cells. The tumors exhibited a variety of MHC phenotypes in vitro. The nature of their phenotypes suggested that these cells were, in fact, capable of independent and abnormal regulation of MHC class 1 genes. However, when maintained in vivo, these same tumor cells expressed measurable levels of all of the appropriate MHC class I antigens. Thus, newly induced tumor cells are capable of abnormal MHC class I antigen expression. However, there was no obvious correlation between the phenotypes exhibited by these tumor cells in vitro and either their phenotype or their tumorigenic potential in vivo.

The major histocompatibility complex and genetic control of antibody response to sheep red blood cells in chickens

The genetic association of the B-F/B-L region of the chicken major histocompatibility complex (MHC) with the antibody response to sheep red blood cells (SRBC) was investigated using three inbred lines of White Leghorn chickens. Two out of the three inbred lines of chickens. J1 and N1, were found to be a low responder to SRBC. Planned matings between the three inbred lines of chickens showed that the genetic regulation of the magnitude of the antibody response to SRBC was associated with the MHC. The low antibody response to SRBC was inherited as a recessive trait linked to the B15 MHC phenotype of the M1 inbred line.

Instability of expression of major histocompatibility antigens in fibroblasts expressing activated ras oncogene: constitutive and interferon-gamma induced class I and class II antigens in a series of clonal isolates of murine fibroblasts transformed by v-Ki-ras

We have examined the expression of major histocompatibility complex (MHC) antigens, constitutive or induced with interferon gamma (IFN-gamma), in a line of C3H mouse embryo fibroblasts (C3H 201) transformed with a helper-virus-free preparation of the Kirsten strain of murine sarcoma virus. C3H 201 cells expressed some class I antigen (H-2Kk) in the absence of added interferon, unlike the parental C3H 10T1/2 cells from which they were derived. However, this declined with (in vitro) passage level after transformation. Treatment with IFN-gamma induced very high expression of H-2Kk at all passage levels. There was no constitutive expression of class II antigen (I-Ak); however, this could be induced by IFN-gamma. Inducibility of I-Ak was found also to be related to the number of passages after transformation; at early passage levels after transformation more I-Ak was induced than after the cells had been allowed to grow for several passages, until at high passage levels little or no I-Ak was induced. This was not due to the presence of a subpopulation of untransformed cells since when the cells were cloned shortly after infection all the resulting clones were transformed. In addition, IFN-gamma at any passage level induced clearly less I-Ak than was found in C3H 10T1/2 cells, in which I-Ak inducibility was high and stable. Twenty-one clones were derived from C3H 201 cells at early passage (less than 8) either from soft agar or from liquid culture. These clones showed a wide variation in MHC antigen phenotype. Many expressed H-2Kk in the absence of IFN-gamma, and all were strongly inducible for H-2Kk. None showed I-Ak in the absence of IFN-gamma. All but two expressed I-Ak after IFN-gamma treatment but, with four exceptions, clearly less than the untransformed line. Four clones derived at late passage (40) resembled the late passage line. The expression of the ras oncogene and tumorigenicity was studied in representative clones; there was no obvious correlation with MHC phenotype, nor with the method of cloning. We conclude from these studies that the expression of MHC antigens by fibroblasts expressing the v-Ki-ras oncogene, either with or without exposure to interferon gamma, is unstable, varying with the number of cell generations from transformation and from clone to clone.

Isoelectric focusing of bovine major histocompatibility complex class I molecules.

The products of the major histocompatibility complex (MHC) loci regulate an individual's immune response to pathogens. Cattle provide an important model to study the relationship between disease susceptibility and MHC haplotype since large half-sibling families are common. The definitive demonstration, however, of a firm relationship between MHC phenotype and disease susceptibility in cattle will require a precise definition of the bovine MHC allelic products. Available reagents for serological characterization of the bovine MHC gene products have not been adequate for these purposes. We have shown that existing mouse monoclonal antibodies and rabbit anti-human antisera precipitate bovine class I molecules, that these structures separate well by one-dimensional isoelectric focusing (1-D IEF), and that immunoprecipitation followed by 1-D IEF allows the detection of bovine class I MHC allelic products. Through this technique, we have identified previously undetected class I products. This approach will facilitate a detailed characterization of the bovine MHC class I gene products.

Why aren't embryos immunologically rejected by their mothers?

Just over 50 years ago, Peter Gorer discovered the major histocompatibility complex (MHC) of the mouse, the H-2 complex (Gorer, 1936a,b; 1937). Since that time, an MHC has been defined for most mammals, and for a variety of lower vertebrate organisms (reviewed in Klein, 1986). The MHC is a set of genes that encodes the information for proteins found on the surface of cells of each individual. The proteins are highly polymorphic, and each individual in the species has a particular set of proteins defining that individual’s tissue type or MHC phenotype. The products of the MHC genes are crucial for the control of a variety of biological functions, including cell-cell interactions in the immune response, tumor and graft rejection, and reproductive success. The best-studied MHC is that of the mouse. A diagram of the current view of the mouse MHC in shown in Figure 1. Extensive work on cloning and sequencing the genes of the H-2 complex, initiated in 1980, has shown that the H-2 complex encodes at least 50 genes (Steinmetz, 1987). The MHC genes code for three different types of proteins, designated Class I, Class II, and Class III. Class I molecules are membrane-bound glycoproteins, all of which have a similar structure, a 35-45,000 molecular weight heavy chain and a 12,000 molecular weight light chain. The heavy chain is encoded in the H-2 complex, but the light chain, 132 -microglobulin, is encoded on mouse chromosome 2. In most species, the Class I genes are clustered at the telomeric end of the MHC, but in the mouse, two Class I genes have been translocated to the centromeric end of the MHC gene complex.

Genetic and viral factors influencing the development of spontaneous leukemia in AKR mice

Factors influencing the development of spontaneous leukemia were studied in a genetic cross that was prepared between leukemia-prone AKR and leukemia-resistant C57BL/6 mice. Two hundred mice of the AKR x (C57BL/6 x AKR)F 1 backcross were examined for (a) the production of endogenous N-ecotropic murine leukemia virus (MuLV), (b) the production of anti-viral antibodies, (c) phenotype at the major histocompatibility complex (MHC), (d) phenotype at the Fv-1(Gpd-1) region, and (e) mortality due to leukemia or other natural causes. Although mice of this cross contained at least one genetic complement of AKR ecotropic MuL V and were expected to produce high levels of infectious virus, a variety of secondary factors influenced the level of MuLV that was detectable in extracellular fluids. The titer of ecotropic MuLV in individual mice was found to relate strongly and simultaneously to the Fv-1(Gpd-1) phenotype and to the titer of anti-viral antibodies in sera. Thus, the levels of infectious MuLV were significantly lower in mice of the Fv-1 n/b genotype and in mice that produced high titers of anti-gp70 antibodies. The production of anti-gp70 antibodies, on the other hand, was regulated independently by the MHC phenotype and the sex of the mouse. High antibody titers were found to be associated with the MHC b/k haplotype and with the female sex. Survival data derived during a 24 month period were used to determine associations between virus expression and death caused by thymic leukemia, nonthymic leukemia, and other natural causes. Regression analysis indicated that genes which mapped within the Fv-1(Gpd-1) region were the most important determinants of the risk of thymic leukemia mortality. Although there was a mild additive effect on mortality associated with the high production of ecotropic MuLV, it appeared that additional factors controlled by genes in the Fv-1(Gpd-1) region were most responsible for the dramatic susceptibility of AKR mice to thymic leukemias. Although the presence of these factors were indicated in this study, their mode of action was not defined. In addition, it was also found that the production of anti-viral antibodies influenced the mortality caused by thymic leukemias. This association, however, could be largely explained by the inverse relationship that existed between the level of detectable ecotropic MuLV and the titer of anti-gp70 antibodies. Last, it was noted that mortality caused by nonthymic leukemias was not significantly influenced by phenotypic variation in either the Fv-1(Gpd-1) region or in the expression of ecotropic MuLV. This finding suggested that leukemias of thymic and nonthymic origin had different etiologies.