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PubMedDate not supplied

Studies of major histocompatibility complex class I/II expression on sequential human heart biopsy specimens after transplantation.

Our previous data indicate that normal human cardiac myocytes do not express detectable levels of major histocompatibility complex (MHC) class II gene products and express only low levels of MHC class I gene products. Examination of heart biopsy samples after transplantation with immunoperoxidase techniques revealed that such myocytes are induced to express high levels of MHC class I/II gene products and that the expression of these gene products appeared to precede histologic evidence of rejection. In efforts to objectively quantitate the level of MHC antigen expression on sequential heart biopsy samples, a radioimmunoassay was set up. Monoclonal antisera was used against human monomorphic MHC class I and II determinants. In addition, to control for the variability in the quantity of biopsy sample, use was made of a monoclonal antisera against human cardiac myosin. A series of three to four sections (4 micron each) of the heart biopsy specimen was treated with each antisera, followed by affinity purified and absorbed iodine 125-labeled goat antimouse immunoglobulin. The mean counts per minute of MHC class I and II was divided by the mean counts per minute obtained with anti-myosin and an index of MHC class I/II derived. Data using such a radioimmunoassay indicate that MHC antigen expression on the heart biopsy specimens does not strictly correlate with histologic rejection grade scores, levels of leukocyte infiltrate, or the immunophenotype of the infiltrating mononuclear cells. Of interest was the finding that an increase in the level of MHC antigen expression occurred before histologic evidence of rejection grades of 3 or greater. In addition, MHC class I antigen expression appeared to increase in heart biopsy samples early during the post-transplant period, followed sequentially by an increase in the level of MHC class II antigen expression. Rejection episodes later during the posttransplant period, however, were accompanied by increased levels of MHC class II antigens. A kinetic analysis of the increase in the levels of MHC class I and II antigens on heart biopsy samples may not only provide a refinement of the histologic scoring of heart biopsy samples for rejection but may also suggest the use of different chemotherapeutic immunosuppressive drug regimens for the treatment of MHC class I as compared with MHC class II dependent rejection episodes.

Antibodies, Monoclonal↗

PubMed1989

MHC class II transcription in different mouse cell types. Differential requirement for protein synthesis between B cells and macrophages.

Although the MHC class II genes are known to be regulated transcriptionally, the relative rates of transcription of the four classical class II genes in different cell types have not been investigated. Using nuclear transcriptional analysis, we have investigated the transcriptional rates of the class II genes in the macrophage cell line WEHI-3, normal bone marrow-derived macrophages, L-929 cells, and two different B cell lymphoma lines. Kinetic analysis of class II transcription in IFN-gamma-treated WEHI-3 cells revealed a 4-h delay, followed by a rapid increase in transcription over the next 20 h. A significant basal level of class II transcription, apparent in bone marrow derived macrophages, was also further enhanced by IFN-gamma treatment. None of the class II genes were transcribed in L cells, whereas all class II genes were transcribed constitutively in the B cell lines. In both B cell lines and macrophages, the four class II genes were found to be transcribed at different rates from one another, but the only gene showing a consistent pattern in multiple experiments was A-alpha, always showing the highest rate. We also investigated the effect of protein synthesis inhibition on class II transcription. Cycloheximide treatment of WEHI-3 cells did not inhibit IFN-gamma-induced transcription of the class II genes within 8 h, suggesting that IFN-gamma acts on pre-existing trans-acting factors, rather than inducing their synthesis. In contrast, treatment of B cells with cycloheximide for 8 h significantly reduced class II transcription, suggesting that, in B cells, continuous synthesis of a labile trans-acting factor is required for constitutive expression. These data support the notion that class II expression in B cells is mediated by trans-acting factors distinct from those found in macrophages.

Animals↗

PubMed1994

MHC class II molecules that lack cytoplasmic domains are associated with the cytoskeleton.

MHC class II molecules, composed of alpha- and beta-chain heterodimers, are required for Ag presentation. The carboxyl-terminal domains of class II molecules are believed to mediate the location of class II in the plasma membrane and are important for signal transduction and Ag presentation. These domains contain typical transmembrane sequences, and cytoplasmic sequences of 12 or 18 amino acids for the alpha- and beta-chains, respectively. We examined these domains to determine whether they linked class II molecules to the actin-based cytoskeleton. Our analyses of class II-cytoskeleton interactions, such as a colocalization with actin filaments during capping, association with the detergent-insoluble cytoskeleton, and direct binding of filamentous actin, revealed that both the cytoplasmic and transmembrane domains contributed to class II interactions with the cytoskeleton. Detergent-extracted and immunoprecipitated full-length class II molecules had quantitatively stronger interactions with the cytoskeleton than did molecules with deleted cytoplasmic domains. A secondary Ab, which was used to cross-link primary Ab bound to class II, up-regulated the class II-cytoskeletal associations. This association was efficiently inhibited by dihydrocytochalasin B, but only partially disrupted by chlorpromazine. The mechanism of interaction with actin filaments after ligation of class II occurred without a measurable increase in filamentous actin levels. This suggested that enhanced class II-cytoskeleton associations involved a rearrangement of existing actin filaments, possibly through the multiple kinases that are activated after class II transmembrane signaling.

Actins↗

PubMed2001

Alterations of HLA class I and II antigen expression in preinvasive, invasive and metastatic cervical cancers.

HLA expression is altered in a large variety of human cancers. We performed immunohistochemical staining on tissues from normal, preinvasive, invasive and metastatic cervical cancer tissues using anti-HLA class I or class II antibody. In tissues from normal squamous epithelium, carcinoma in situ (CIS) and microinvasive carcinoma (MIC), the expressions of HLA-B, C heavy chains and class II heavy chain were significantly decreased as disease progressed. When the expression patterns were compared between primary and metastatic squamous cell carcinoma (SCC) lesions, statistically significant down-regulation of HLA class I and class II antigen in metastatic lesions was observed. The rates of HLA-B, C heavy chains and class II heavy chain expressions were all significantly down-regulated compared to the down-regulation rate of class I beta2-microglobulin (beta2m) in invasive squamous lesions, and the expressions of class II heavy chain in metastatic lesions was decreased further than that in primary lesions. Unlike SCC, the degree of HLA class I and class II loss was not evident as disease progressed in early stage of adenocarcinoma. In invasive adenocarcinoma lesions, only the expression of HLA-B, C heavy chains was decreased and no differences were seen in HLA-B, C heavy chain expression patterns between primary and metastatic lesions. These results suggest that alterations of HLA class I and II expressions seem to occur at a particular step in cervical cancer development and depend on tissue types: when the tumor becomes invasive and starts to metastasize.

Antibodies, Monoclonal↗

PubMed1989

Identical peptides recognized by MHC class I- and II-restricted T cells.

Previous data from many groups show that both class I and class II-restricted T cells recognize short synthetic peptides in the context of their respective MHC molecules (9-18), all of the peptides described to date are restricted to only a single class of MHC molecules; however, structural homology between the class I and II MHC molecules and the use of similar TCRs by class I and II-restricted T cells suggest that antigen recognition mechanisms are similar in both systems. To directly compare antigen recognition in the two systems, we analyzed peptides for the ability to function in both a class I and II-restricted system and found that seven of seven individual peptides tested stimulate both class I and II-restricted T cell responses. In addition, two of the peptides can function in different species stimulating both human class I and murine class II T cell responses. Thus, the process of T cell recognition of antigen in the context of MHC molecules was highly conserved in evolution not only between the class I and class II MHC systems, but also between the murine and human species.

Animals↗

PubMed1998

Dendritic cell/macrophage precursors capture exogenous antigen for MHC class I presentation by dendritic cells.

Presentation of MHC class I antigens by professional antigen-presenting cells (APC) is an important pathway in priming cytotoxic T lymphocyte responses in vivo. This study sought to identify the nature of the professional APC responsible for indirect class I presentation by examining a special feature of professional APC, namely their ability to process exogenous forms of antigen for class I presentation. Incubation of highly purified bone marrow-derived precursor cells with chicken ovalbumin (OVA) led to the efficient presentation of the major class I-restricted OVA determinant by mature dendritic cells (DC), but not by macrophages (Mphi) derived from the precursor population. DC as well as macrophages were, however, able to mediate class II presentation of OVA, suggesting that macrophages were deficient in class I processing but not in capturing exogenous OVA. The majority of mature DC, i.e. over 80 %, generated from the precursor cells pulsed with OVA, presented the class I OVA epitope. Upon maturation, class I presentation of OVA by DC was greatly reduced, suggesting that class I processing of exogenous antigen is modulated during DC maturation in a manner similar to class II antigen processing. This study shows that bone marrow-derived DC/ME progenitors capture exogenous antigen for class I presentation, and that cells of the DC lineage can be functionally distinguished from cells of the macrophage lineage based on their ability to process exogenous antigen for class I presentation.

Amino Acid Sequence↗

PubMed2001

Anorexia nervosa and social class.

OBJECTIVES: (1) To examine social class status of female patients with anorexia nervosa presenting over a 33-year period; (2) to identify any differences in clinical features between the social classes. METHOD: Retrospective survey using comprehensive clinical database of patients referred to a national specialist center for the assessment and treatment of anorexia nervosa. Social class was defined using UK Registrar General's classification of father's occupation. Statistical methods included initial univariate analyses and subsequent ordinal logistic regression. RESULTS: (1) Social class distribution was consistently weighted toward social classes 1/2. (2) Possible clinical indicators examined included low body weight, binge eating, and consequent weight-regulatory behaviors such as vomiting and laxative and diuretic misuse. These clinical features and their distribution proved to be similar across the social groups. Clinically rated quality of family relationships and types of family constellations were also consistent across the social classes. (3) Dieting prodromata and onset of the disorder occurred at younger ages in social classes 1/2. (4) A modest shift in social class distribution over time was apparent, with slightly more patients presenting post-1985 likely to come from lower social classes. Claims that the social class distribution is a product of referral patterns and acceptances are disputed. CONCLUSION: We suggest that the social class bias reflects a sociocultural influence; a product of the disorder significantly often arising as an avoidant response to the conflict between social class-related family values/attitudes and adolescent turbulence within that family.

Adult↗

PubMed1991

Comparison of class I- and II-restricted T cell recognition of the identical peptide.

There is structural and functional evidence that both class I- and II-restricted T cells recognize short processed peptides bound to MHC molecules. Although the structural conformation of bound peptides remains unknown, no evidence of distinct structural motifs of class I- or class II-restricted peptides has been described. Conversely, two algorithms proposed to predict T cell epitopes, and based on primary amino acid sequence or tertiary structure, are both compatible with many observed class I- and class II-restricted peptides. We previously identified eight class I-restricted peptides which were also recognized by class II-restricted T cells. Based on functional and direct binding studies, additional examples of peptides with both class I and II restrictions have been identified. In this study, we have directly compared the fine specificity of T cell recognition of a single epitope in a single mouse strain in the context of both class I- and class II-restricted responses. Based on a panel of analogue peptides with amino acid substitutions and peptides of various lengths, we observed several striking similarities in the recognition patterns of both class I- and class II-restricted T cells. In addition, some characteristics of recognition were different in the two systems indicating that the recognition processes were similar but not identical.

Amino Acid Sequence↗

PubMed1995

Characterization of mature and immature RadLV-induced thymic T-cell lines for tumorigenesis and MHC-class-I gene expression.

Class-I-MHC molecules are divided into class-Ia molecules, which play major roles in recognition of virus-infected cells, graft rejection and immune responses against tumors, and class-Ib molecules, which are less polymorphic and may be responsible for presenting unique classes of peptides. Our report characterizes RadLV-induced thymic T-cell lines that differ both in their tumorigenic potential and in the level of protein for class-Ia and TL genes. The PD1.1 cell line is CD4-CD8+ and expresses relatively high levels of class-I as compared with the CD4+CD8+ PD1.2 cell line. These class-I-expression levels correlate with thymocytes and splenic T cells of the same phenotype, except that normal cells fail to express TL3b. Interferon-treated PD1.2 cells demonstrate significantly lower levels of class-I expression than do interferon-treated PD1.1 cells, and were shown to contain large amounts of degraded class-I mRNA, at least some of which was TL in origin. These RNA products were not detected in PD1.1 cells, suggesting the existence of a mechanism controlling cell-specific and gene-specific mRNA stability. Such RadLV-induced cell lines provide a means for obtaining stage-specific T cells, which can be used for studying the regulation of class-I gene expression during T-cell differentiation, as well as factors that differentially regulate class-Ia and class-Ib expression and are potentially useful for studying T-cell differentiation in general.

Animals↗

PubMed1997

Social class differences in women's fat and fibre consumption: a cross-national study.

This study focuses on social class variation in the intake of fat and fibre in Maastricht, Liège and Aachen, based on food frequency questionnaires of 849 women from nuclear families with schoolgoing children. In Maastricht and Liège higher-middle class women consumed less fat than working class women, while in Aachen no class difference was apparent. The intake of fibre was highest among the higher-middle class women, although this tendency was not significant in Aachen. Analysis of food groups that contribute to the intake of fat and fibre revealed that not all food groups showed this pattern. Higher-middle class women consumed less bread, less potatoes and more cheese than working class women. Moreover, they chose more often high-fat cheese and fats. Yet, working class women consumed more meat, milk and fats, and less grain, fruit and vegetables. In general, social class variations in fat and fibre intake were uniform across the cities, although in Aachen class differences were small or absent. In conclusion, these results suggest that the diet of higher-middle class women is more in accordance with the dietary recommendations regarding fat and fibre than the diet of working class women.

Adult↗

PubMed1999

Quantification of epitope-specific MHC class-II-restricted T cells following lymphocytic choriomeningitis virus infection.

CD4(+) T cells are critical for the control of many viruses; however, the numbers of virus-specific CD4(+) cells that are expanded following infection are unknown. We have addressed this issue by enumerating virus-specific, MHC class-II-restricted T cells following infection of mice with lymphocytic choriomeningitis virus (LCMV). We have found that the numbers of T cells that produce interferon-gamma in response to stimulation with three different class-II-restricted LCMV epitopes increase from undetectable numbers in noninfected animals to between 4 x 10(5) and 2 x 10(6) cells per spleen at the peak of the T cell response. This contrasts with the numbers of virus-specific class-I-restricted T cells which expand to 1 x 10(7) to 2 x 10(7) cells per spleen during the same time period. We could not reproducibly detect virus-specific class-I-restricted or class-II-restricted T cells that produced interleukin-4 at any time following LCMV infection, indicating that infection with this virus induces a predominantly type 1 cytokine response. In contrast to the rapid decrease in the numbers of class-I-restricted T cells, the numbers of LCMV-specific class-II-restricted T cells declined gradually following the peak of the T cell response. We demonstrate, therefore, that following infection with LCMV there is expansion of both class-I-restricted and class-II-restricted virus-specific T cells; however, the degree of expansion of class-II-restricted T cells is substantially less than that observed for class-I-restricted cells. Furthermore, the downregulation phase of the class-II-restricted response is protracted compared with the precipitous contraction of the antiviral CD8(+) T cell response.

Amino Acid Sequence↗

PubMed1994

Organization of Mhc class II B genes in the zebrafish (Brachydanio rerio).

Using three genomic phage libraries, we isolated 26 clones from the zebrafish MHC class II B region. By restriction mapping, the clones could be arranged into six clusters, most clusters consisting of several overlapping clones. The combined clusters cover a total of 161 kb of the zebrafish class II region. Hybridization with specific probes demonstrated the presence in the clusters of two class II A and six class II B genes. Sequencing of the B genes revealed that they represented six different families of class II loci. Only two of the class II B and one of the class II A genes are complete; the others are truncated pseudogenes. Only one of the class II B loci shows extensive restriction fragment length polymorphism. This is also the only locus found to be transcribed in organs with large numbers of lymphoid or myeloid cells. The zebrafish class II genes have promoter regions with sequence elements found previously in mammalian genes and known to be involved in regulation of expression. The exon-intron organization of the zebrafish class II genes is similar to that of the mammalian genes, but the introns are characteristically short, ranging in length from 74 to 362 bp. The distances between A and B genes in a given pair are also short, but the distances between B genes are as long as or longer than those between mammalian class II B genes. All of the zebrafish class II B genes appear to have arisen by duplication and diversification of a single ancestral B gene after the separation of bony fishes from other vertebrate taxa.

Amino Acid Sequence↗

PubMed2000

Trends in social class inequalities in health status, health-related behaviors, and health services utilization in a Southern European urban area (1983-1994).

BACKGROUND: The objective of this study was to describe the evolution of social class inequalities in Barcelona (Spain) residents in perceived health status, health-related behaviors, and utilization of health services between 1983 and 1994. METHODS: The information was obtained from the Health Interview Surveys conducted in 1983, 1986, 1992, and 1994 in Barcelona. In this study we included noninstitutionalized people ages >14 years. Social class was obtained from the Spanish adaptation of the British Registrar General classification. We studied health status, health-related behaviors, and health services utilization variables. Age-adjusted percentages and the relative index of inequality were obtained. RESULTS: Of the health status variables, having been confined to bed and acute restriction of activity in the 2 weeks prior to the interview showed an increase in inequalities by social class in 1994. The pattern of chronic conditions by social class in men did not change between 1983 and 1994. Women had a higher prevalence of chronic conditions and the inequalities among social classes had increased. In men there were no social class inequalities in smoking in 1983. In 1992 and 1994 smoking was more prevalent in men of social classes IV and V. In women, smoking was more prevalent in social classes I and II in 1983 than in social classes IV and V, something that had changed by 1994. Lack of usual physical activity in men was always more prevalent in social classes I and II, and this difference increased since more people of advantaged classes moved into inactivity. Health services utilization showed no inequalities in the years studied. CONCLUSION: The changing pattern according to social class of smoking and physical activity practice needs to be taken into account by policy-makers and public health workers.

Adolescent↗

PubMed2001

Trends in cigarette smoking in Spain by social class.

OBJECTIVE: . The aim of this study was to evaluate smoking trends among Spanish men and women by social class between 1987 and 1997. METHODS: We used secondary analysis of the National Health Interview Surveys of 1987, 1993, 1995, and 1997. The main outcome measures were prevalence of smoking, smoking cessation activity (quit ratio), and smoking initiation in the manual and nonmanual social class in each year and smoking prevalence ratio, smoking cessation ratio, and smoking initiation ratio in 1997 versus 1987 in each social class. RESULTS: Among men ages 25 years and older the prevalence of smoking in both the manual and the nonmanual social class decreased between 1987 and 1997 in all age groups, and the relative magnitude of the decrease was always greater in the nonmanual social class. In contrast, among women the prevalence of smoking increased in both social classes: in the 25- to 44-year age group the smoking prevalence ratios in 1997 versus 1987 were 1.20 in the nonmanual social class and 1.61 in the manual social class, while in the 45- to 64-year age group the prevalence ratios were 2.52 and 2.15, respectively. The quit rate among men increased in both social classes in all age groups between 1987 and 1997; in contrast, among women the quit rate increased only among those ages 25 to 44 years in the nonmanual social class. Smoking prevalence for people ages 16 to 24 years--smoking initiation--decreased among men and women between 1987 and 1997 in both social classes. CONCLUSIONS: Smoking trends in Spain by social class have differed among men and women. The findings are considered in the context of policies and programs aimed at reducing smoking.

Adolescent↗

PubMed1989

Evidence that IFN-gamma does not affect MHC class II gene expression at the post-transcriptional level in a mouse macrophage cell line.

Mouse class II major histocompatibility complex genes have been shown to be regulated at the level of transcription for both tissue-specific and inducible expression. In particular, IFN-gamma induction of the class II genes has been shown to occur at the transcriptional level, although the role that additional post-transcriptional mechanisms of regulation may play in this induction is not known. To evaluate IFN-gamma effects on transcriptional and post-transcriptional events of class II gene expression, we examined the rate of decline of class II transcription, steady-state mRNA, and cell surface protein following the removal of IFN-gamma from maximally stimulated WEHI-3 cells (an IFN-gamma inducible, myelomonocytic cell line). We determined that transcription of class II genes almost completely returned to baseline levels eight hours after removal of IFN-gamma. However, the steady-state level of class II mRNA's required 4 days, and membrane Ia expression required 5 days to return to baseline levels. This decay was linear and allowed us to determine a half-life value of 16-20 h for class II transcripts. These data demonstrate that, following removal of IFN-gamma from fully stimulated cells, transcription of the class II genes declined rapidly, but mRNA was quite long-lived. We also assessed the class II mRNA stability in unstimulated WEHI-3 cells and the B-cell lymphoma. A20/2J, by actinomycin D treatment and northern blot analysis. In agreement with the IFN-gamma washout experiments, transcripts from all four class II genes were quite long-lived in these cell types, with a half-life greater than ten hours. These data support the concept that IFN-gamma acts primarily at the level of class II transcription and argues against IFN-gamma playing a major role in post-transcriptional modulation of class II expression.

Animals↗

PubMed1996

Characterization of class II A and B genes in a gynogenetic carp clone.

A prerequisite for carrying out functional studies on major histocompatibility complex (Mhc) molecules of fish is the availability of genetically well-defined homozygous strains. Previously we have applied gynogenetic reproduction to generate isogenic carp, denoted clone A410. This clone has recently been demonstrated to express a single class I gene, Cyca-UA1(*)01, and in the present study two class II B and two class II A transcripts were obtained. The two class II B transcripts, Cyca-D(CB3)B and Cyca-D(CB4)B, as well as the class II A transcripts, Cyca-D(10A)A and Cyca-D(15A)A, appear to be bona fide class II transcripts, based on the presence of conserved protein characteristics of the inferred class II molecules. With the isolation of class II A sequences, representatives of all major classes of Mhc genes have been identified in the carp. To assess the relationship between the different class II genes, segregation studies, comparison of cDNA and intron 1 sequence data, and phylogenetic analyses were undertaken. These showed that the class II B transcripts, Cyca-D(CB3)B and Cyca-D(CB4)B, are derived from related, closely linked loci. In addition, these studies indicated that the previously described Cyca-DAB*01 and Cyca-DAB*02 are also closely linked, but that this linked pair segregates independently from the Cyca-D(CB3)B and Cyca-D(CB4)B loci. The class II A transcripts are most likely derived from separate loci and do not represent alleles, as they were found not to segregate in the individuals of the clone which was generated by meiogenetic gynogenesis.

Amino Acid Sequence↗

PubMed1999

Evolution of the Mhc class I region: the framework hypothesis.

A comparison of the major histocompatibility complex (Mhc) region between human and mouse highlights both stability and differences. The class II and class III regions are orthologous; they probably existed in the ancestor in a similar organization and were not subjected to major rearrangement. The class I genes, by contrast, are definitely paralogous, having been reorganized several times. As long as only class I genes were identified, the class I regions of human and mouse were difficult to compare directly. The identification of non-class I genes has allowed a comparative map to be drawn, which shows that the class I region is orthologous between human and mouse as well. The lack of orthology specifically applies to the class I sequences. However, the comparative map shows that the non-orthologous class I sequences occupy homologous locations with regard to the conserved genes. I propose a model to explain this paradox. The conserved genes may represent samples of a dense "framework" of genes whose alterations are deleterious. The homologous positions occupied by class I genes would thus represent the few permissive places allowing major perturbations. The evolution of the class I sequences, by duplication and deletion, independently in the two species, has taken place within the scope defined by the framework: insertion at the permissive places, and expansion by creation of class I-related DNA by duplication, thus pushing back the boundaries of the framework.

Amino Acid Sequence↗

PubMed2006

Molecular identification, polymorphism, and expression analysis of major histocompatibility complex class IIA and B genes of turbot (Scophthalmus maximus).

Major histocompatibility complex (MHC) class II has a central role in the adaptive immune system by presenting foreign peptides to the T-cell receptor. The full lengths of MHC class II A and B cDNA were cloned from turbot by homology cloning and rapid amplification of cDNA ends polymerase chain reaction (RACE PCR), and genomic organization, molecular polymorphism, and expression of turbot class IIB gene were examined to study the function of class IIB gene in fish. The deduced amino acid sequence of turbot class II A (GenBank accession no.DQ001730) and turbot class IIB (GenBank accession no. DQ094170) had 69.8%, 67.6%, 65.5%, 59.2%, 54.5%, 52.8%, 46.2%, 46.6%, 28.3%, 28.5%, 22.2% identity and 71.5%, 70.7%, 67.1%, 68.4%, 46.7%, 53.5%, 46.7%, 50.0%, 25.2%, 29.2%, 27.6% identity with those of Japanese flounder, striped sea bass, red sea bream, cichlid, rainbow trout, Atlantic salmon, carp, zebrafish, nurse shark, mouse and human, respectively. Eleven class IIB alleles were identified from three turbot individuals. The amino acid sequence of turbot class IIB designated as Scma-DAB*0101 had 86.9%, 88.6%, 88.6%, 89.4%, 87.8%, 86.9%, 84.1%, 86.5%, 87.3%, 77.1%, and 86.9% identity with those of turbot class IIB 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 (Scma-DAB*0201- Scma-DAB*1201), respectively. Six different class IIB alleles observed in a single individual may infer the existence of three loci at least. Semiquantitative reverse transcriptase PCR (RT-PCR) demonstrated that turbot class IIA and B were ubiquitously expressed in normal tissues. Challenge of turbot with pathogenic bacteria, Vibrio anguillarum, resulted in a significant decrease in the expression of MHC class IIB mRNA from 24 h to 48 h after infection in liver and head kidney, and a significant decrease from 24 h to 72 h after infection in spleen, followed by an increase after 96 h, respectively.

Amino Acid Sequence↗