Gene organization of DC and DX subregions of the human major histocompatibility complex

The Regulation of Immunity

In their AAI President's Addresses reproduced in this issue, Jeremy M. Boss, Ph.D. (AAI '94; AAI president 2019–2020), and Jenny P.-Y. Ting, Ph.D. (AAI '97; AAI president 2020–2021), welcomed attendees to the AAI annual meeting, Virtual IMMUNOLOGY2021™. Due to the SARS-CoV-2 pandemic and the cancellation of IMMUNOLOGY2020™, Dr. Boss and Dr. Ting each presented their respective president's address to open the meeting.

Sequencing and genetic analysis of a bovine DQB cDNA clone

A BoLA-DQB cDNA clone (BoLA-DQ beta-1) was isolated by screening a bovine lymphoblastoid cDNA library with a HLA-DQB genomic clone. The DNA and predicted protein sequences were compared to class II sequences from cattle and other species. BoLA-DQ beta-1 has 92.0% similarity to the coding regions of two previously sequenced BoLA-DQB genomic clones and 69.6% similarity to a BoLA-DR beta pseudogene. However, the first domain encoded by BoLA-DQ beta-1 has 94 amino acids; one more than the predicted size of the products encoded by two previously sequenced bovine DQB genes (BoDQ beta-Q1 and BoDQ beta-Y1). Comparing all coding regions, BoLA-DQ beta-1 has greater nucleotide similarity to HLA-DQB sequences than to I-A beta, HLA-DRB and I-E beta sequences. Like the HLA-DQB gene product, the cytoplasmic domain of the predicted protein encoded by BoLA-DQ beta-1 is eight amino acids shorter than that of I-A beta, HLA-DRB and I-E beta molecules. Six clone-specific amino acid substitutions were identified in the beta 1 domain of BoLA-DQ beta-1, including an unusual cysteine residue at position 13 which is believed to be positioned on a beta-strand and face into the antigen recognition site. Southern blot analysis of PvuII-digested genomic DNA from a paternal half-sibling family (sire, and six dam-offspring pairs) using BoLA-DQ beta-1 as a probe, revealed five allelic PvuII RFLP patterns, including two patterns not previously described, that cosegregated with serologically-defined BoLA-A (class I) alleles. The evolution, polymorphism and function of a transcriptionally active BoLA-DQB gene can now be readily studied using this DQB cDNA clone as a source of allele and locus-specific oligonucleotide primers.

Cloning of the bovine major histocompatibility complex class II genes

Class II genes of the bovine major histocompatibility complex (MHC) have been cloned from a genomic library. The library was constructed in the bacteriophage lambda vector EMBL3 and comprises approximately 10 times the equivalent of the haploid genome. Half the library was screened with the human DQA, DQB, DRA and DRB cDNA probes. Of the 100 positively hybridizing phage clones, 37 were eventually fully characterized and mapped by means of Southern blot analysis. The exons encoding the first, second and transmembrane domain of all different A and B genes were subcloned and mapped in more detail. These analyses showed that these 37 clones were derived from five different A and 10 different B genes. The hybridization studies indicate that we have cloned and mapped two DQA genes, one DRA gene, two other A genes, four DQB genes, three DRB genes and three other B genes. Since the library was made from a heterozygous animal, this would suggest that there are at least one DQA, one DRA one other undefined A, two DQB, two DRB and one or two other undefined B genes in the haploid genome of Holstein Friesian cattle.

Genomic hybridization of bovine class II major histocompatibility genes: 1. Extensive polymorphism of DQ alpha and DQ beta genes

Class II genes of the bovine major histocompatibility complex (MHC) were investigated by Southern blot analysis using human cDNA probes for DQ alpha, DQ beta, DR alpha and DR beta. The presence of a DQ-like and a DR-like subregion in cattle was clearly indicated. Highly polymorphic restriction fragment patterns were obtained when genomic DNA, digested with any one of the BamHI, EcoRI or PvuII restriction enzymes, was hybridized with the DQ alpha and the DQ beta probe. The polymorphisms were interpreted genetically by analysing five paternal half-sib families of the Swedish Red and White breed. The material comprised, besides the bulls, 28 offspring and their dams. The analysis resolved 9 and 12 allelic variants of DQ alpha and DQ beta respectively. Thus, this investigation establishes a method for routine typing of MHC class II gene polymorphism in cattle. The results were entirely consistent with close linkage of DQ alpha and DQ beta since no recombinant was found and since alleles at these loci occurred in complete linkage disequilibrium in the material investigated. Close linkage between DQ and the blood group locus M, which has previously been found to be closely linked to the serologically defined BoLA-A locus, was also indicated. In this study DNA was isolated from frozen semen samples of dead bulls, which shows that this type of analysis will be useful in genetic investigations in cattle breeds, where artificial insemination is practised.

HLA class II transgenic mice mimic human inflammatory diseases

Population studies have shown that among all the genetic factors linked with autoimmune disease development, MHC class II genes on chromosome 6 accounts for majority of familial clustering in the common autoimmune diseases. Despite the highly polymorphic nature of HLA class II genes, majority of autoimmune diseases are linked to a limited set of class II-DR or -DQ alleles. Thus a more detailed study of these HLA-DR and -DQ alleles were needed to understand their role in genetic predisposition and pathogenesis of autoimmune diseases. Although in vitro studies using class-II restricted CD4 T cells and purified class II molecules have helped us in understanding some aspects of HLA class-II association with disease, it is difficult to study the role of class II genes in vivo because of heterogeneity of human population, complexity of MHC, and strong linkage disequilibrium among different class II genes. To overcome this problem, we pioneered the generation of HLA-class II transgenic mice to study role of these molecule in inflammatory disease. These HLA class II transgenic mice were used to develop novel in vivo disease model for common autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, insulin-dependent diabetes mellitus, myasthenia gravis, celiac disease, autoimmune relapsing polychondritis, autoimmune myocarditis, thyroiditis, uveitis, as well as other inflammatory disease such as allergy, tuberculosis and toxic shock syndrome. As the T-cell repertoire in these humanized HLA transgenic mice are shaped by human class II molecules, they show the same HLA restriction as humans, implicate potential triggering mechanism and autoantigens, and identify similar antigenic epitopes seen in human. This review describes the value of these humanized transgenic mice in deciphering role of HLA class II molecules in immunopathogenesis of inflammatory diseases.

CD4 T Cells Play Major Effector Role and CD8 T Cells Initiating Role in Spontaneous Autoimmune Myocarditis of HLA-DQ8 Transgenic IAb Knockout Nonobese Diabetic Mice

In humans, spontaneous autoimmune attack against cardiomyocytes often leads to idiopathic dilated cardiomyopathy (IDCM) and life-threatening heart failure. HLA-DQ8 transgenic IAb knockout NOD mice (NOD.DQ8/Ab(0); DQA1*0301, DQB1*0302) develop spontaneous anticardiomyocyte autoimmunity with pathology very similar to human IDCM, but why the heart is targeted is unknown. In the present study, we first investigated whether NOD/Ab(0) mice transgenic for a different DQ allele, DQ6, (DQA1*0102, DQB1*0602) would also develop myocarditis. NOD.DQ6/Ab(0) animals showed no cardiac pathology, implying that DQ8 is specifically required for the myocarditis phenotype. To further characterize the cellular immune mechanisms, we established crosses of our NOD.DQ8/Ab(0) animals with Rag1 knockout (Rag1(0)), Ig H chain knockout (IgH(0)), and beta(2)-microglobulin knockout (beta(2)m(0)) lines. Adoptive transfer of purified CD4 T cells from NOD.DQ8/Ab(0) mice with complete heart block (an indication of advanced myocarditis) into younger NOD.DQ8/Ab(0) Rag1(0) animals induced cardiac pathology in all recipients, whereas adoptive transfer of purified CD8 T cells or B lymphocytes had no effect. Despite the absence of B lymphocytes, NOD.DQ8/Ab(0)IgH(0) animals still developed complete heart block, whereas NOD.DQ8/Ab(0)beta(2)m(0) mice (which lack CD8 T cells) failed to develop any cardiac pathology. CD8 T cells (and possibly NK cells) seem to be necessary to initiate disease, whereas once initiated, CD4 T cells alone can orchestrate the cardiac pathology, likely through their capacity to recruit and activate macrophages. Understanding the cellular immune mechanisms causing spontaneous myocarditis/IDCM in this relevant animal model will facilitate the development and testing of new therapies for this devastating disease.

THE TORTUOUS JOURNEY OF A BIOCHEMIST TO IMMUNOLAND AND WHAT HE FOUND THERE

After starting out to become a physician, by a series of accidents I found myself at NIH in 1951 during its most productive growth phase. At age 26, I had a fully funded, independent laboratory and did not know what to work on. With advice from colleagues, I initiated a study of how penicillin kills bacteria. Twenty years later, my lab had outlined the structure and biosynthesis of the peptidoglycan of bacterial cell walls and had discovered that penicillin inhibited the terminal step in its biosynthesis catalyzed by transpeptidases. I then switched fields, moving to Harvard in 1968 and beginning the study of human HLA proteins. Twenty-five years later, the last half of which was spent in a stimulating collaboration with the late Don Wiley, our labs had isolated, crystallized, and elucidated the three-dimensional structures of these molecules and shown that their principal function was to present peptides to the immune system in initiating an immune response. More recently, the laboratory has focused on natural killer cells and their roles in peripheral blood and in the pregnant uterine decidua. It has been a wonderful scientific journey.

A Spontaneous Model for Autoimmune Myocarditis Using the Human MHC Molecule HLA-DQ8

Genome-wide analyses have shown that the MHC class II region is the principal locus that confers susceptibility to a number of human autoimmune diseases. Due to the high degree of linkage disequilibrium across the MHC, it has been difficult to dissect the contribution of individual genes to disease susceptibility. As a result, intensive efforts have been made to generate mice transgenic for human class II molecules as models of autoimmune disease. However, in every case, additional manipulations-such as immunization with Ag in adjuvant, expression of immunostimulants on target tissues, or coexpression of TCR transgenes-have been required to induce disease. In this study, we show that expression of the human HLA-DQ8 (DQA1*0301/DQB1*0302) molecule alone in three lines of transgenic nonobese diabetic murine class II-deficient (mII(-/-)) mice results in the spontaneous development of autoimmune myocarditis. The disease shares key features of human myocarditis and was characterized by lymphocytic infiltrates in the myocardium and cardiac myocyte destruction, circulating IgG autoantibodies against cardiac myosin heavy chain, and premature death due to heart failure. We demonstrate that myocarditis could be transferred into healthy HLA-DQ8(+)RAG-1(-/-)mII(-/-) nonobese diabetic recipients with lymphocytes, but not sera. It has been widely thought that autoimmune myocarditis is of infectious etiology, with the immune responses arising secondary to cardiac damage from pathogens. These studies provide direct experimental evidence that spontaneous autoimmune myocarditis can occur in the absence of infection and that expression of HLA-DQ8 confers susceptibility to this organ-specific autoimmune disease.

HLA-DQA1 polymorphism in autochthonous Basques from Navarre (Spain): genetic position within European and Mediterranean scopes

In this work, a sample of 112 individuals from an autochthonous Basque population (Northern Navarre, Spain) were typed at the DNA level for the HLA-DQA1 locus, with the aim of characterizing its polymorphism and analyzing the genetic relationships of Basque Navarrese with other Caucasian populations. Northern Navarre is a neighboring area with Guipúzcoa, a province located in the core of the Basque territory having the highest proportion of Basque-speakers. In Navarrese population, the most frequent alleles were DQA1*01 (0.375) and DQA1*02 (0.259). Frequency clines for both DQA1*0103 allele and DQA1*04* allele cluster (including DQA1*0401, DQA1*0501 and DQA1*0601) among the European and Mediterranean populations considered are reported for the first time. Furthermore, a spatial structuring previously described for DQA1*02 allele is corroborated. The information provided by the highly polymorphic HLA-DQA1 locus was stressed by using genetic distances and non-metrical multidimensional scaling (MDS). The analysis of genetic relationships among populations showed a high genetic affinity between the Basque subpopulations of Northern Navarre and Guipúzcoa, which in turn tended to plot separately from the remaining European and Mediterranean populations. In the same way, the Basques showed no clear relationship to North African populations, as postulated in several previous HLA studies. The observed genetic heterogeneity seems to be conditioned by the high frequencies of the DQA1*02 allele in Basques from Guipúzcoa and North Navarre. These two subpopulations seem to show low levels of admixture with other non-Basque neighboring populations, probably because of their deeply rooted ethnicity and the existence of a linguistic barrier to random mating.

Cryptic determinants and promiscuous sequences on human acetylcholine receptor: HLA-dependent dichotomy in T-cell function

Experimental autoimmune myasthenia gravis can be induced in some strains of mice and rats by immunizing with acetylcholine receptor. Also, epidemiologic studies demonstrate an MHC linkage of myasthenia gravis in the man. In order to obtain direct experimental evidence for the influence of the genes of the MHC complex in the development of myasthenia gravis, we used mice transgenic to individual HLA molecules. We observed an increased susceptibility to the disease in HLA DQ8 transgenic mice compared to HLA DQ6 transgenic mice ( J. Immunol. 160:4169; 1998). These mice lacked endogenous mouse class II molecules. In the present study we mapped the cryptic and dominant sequences on the extra cellular region of human acetylcholine receptor. Although some epitopes (e.g., alpha11-30, alpha141-160, alpha171-190) were common between DQ8 and DQ6 transgenic mice, several others were disparately recognized. We also found a functional dichotomy in T cells from mice differing by one MHC molecule (HLA DQ8 or DQ6) when primed by sequences immunodominant in DQ8 and DQ6 tg mice. Differential disease manifestation in the two different HLA transgenic mice could be explained not only by differential recognition of peptides by these antigen presenting molecules, but also by the difference in the functional profile of T cells generated when primed by promiscuous sequence regions.

Absence of in vivo DNA-protein interactions in the DQA2 and DQB2 promoter regions

The DQ subregion of the human major histocompatibility complex (HLA) contains two pairs of loci: the DQA1/B1 genes (hereafter called DQ1), coding for the DQ molecules, and the DQA2/B2 pseudogenes (hereafter called DQ2). These pseudogenes are highly homologous to the functional DQ1 genes and they have no apparent abnormal features in their sequences that could prevent their activity. Only recently a low expression of the DQA2 gene has been observed whereas the DQB2 transcript was never found. The comparison between the DQ1 and DQ2 regulatory sequences revealed several differences in their W, X, and Y cis-acting elements. To examine the DNA/protein interactions in the DQ promoter regions, we performed in vivo footprinting experiments. Whereas the functional DQ1 loci showed a series of DNA-protein contact points in the X and Y boxes, the promoters of the DQ2 pseudogenes displayed an unoccupied phenotype. These findings suggest that the very low level of DQA2 expression and the apparent lack of DQB2 activity are caused by the reduced binding affinity of specific transcription factors.

Isolation and rapid identification of an abundant self-peptide from class II HLA-DRB1*0401 alleles induced by measles vaccine virus infection

Class II HLA-DR genes play an important role in the immune response to viral antigens. The effect of measles vaccine virus (MVV) infection on the induction of self-peptides presented by HLA-DR molecules during the immune response to viral infection is poorly known. Here, we describe a strategy for isolation and rapid sequence determination of an MVV-inducible class II bound peptide from a membrane protein (Leu-13). Peptides bound to HLA-DR4 (DRB1*0401 peptide complex) were eluted from immunoaffinity-purified HLA-DR4, peptides were differentially screened by MALDI-TOF-MS and subsequently sequenced by post source decay (PSD)-MALDI-TOF-MS. Human B-cells infected with MVV demonstrated an enhanced pattern of self-peptide production after MVV infection. This relatively simple analytical protocol provides a sensitive method for the direct identification of peptides associated with MHC class II DR molecules. More broadly, this same approach can be used to identify sequences of specific MVV processed peptides presented by any class II MHC DR molecule.

Sequence-based typing of HLA class II DQB1

Due to the expanding number of known HLA class II DQB1 alleles, high-resolution oligotyping is becoming ineffective, therefore a sequence-based typing (SBT) strategy was developed to provide rapid and definitive typing of HLA-DQB1. HLA-DQB1*02, *03, *04, *05, and *06 alleles were individually amplified by polymerase chain reaction (PCR) using exon 2 group-specific primers. Forward and reverse PCR primers were tailed with M13 universal and M13 reverse sequences, respectively. Subsequent bi-directional cycle-sequencing was carried out using Cy5.5-labeled M13 universal primer and Cy5.0-labeled M13 reverse primer. Automated sequencing was performed in 30 min using a Visible Genetics, Inc. (VGI) MicroGene Clipper Sequencer. Full concordance was observed between this SBT method and oligotyping among 151 individuals.

NOD background genes influence T cell responses to GAD 65 in HLA-DQ8 transgenic mice

The major histocompatibility complex (MHC) genes play a significant role in the predisposition to insulin-dependent diabetes mellitus or type 1 diabetes. HLA-DQ8 (DQB1*0302, DQA 1*0301) genes have been shown to have the highest relative risk for human type 1 diabetes. To develop a "humanized" mouse model of diabetes, HLA-DQ8 was transgenically expressed in mice lacking endogenous class II genes. Since non-MHC background genes of the NOD influence the disease process, AP"/DQ8 mice were mated with the NOD strain and backcrossed to generate Abeta degree/DQ8/NOD mice. These mice have DQ8 as the sole MHC class II restriction element with NOD background genes at the N 2 generation. The DQ8 transgenic mice were used to identify T cell epitopes on glutamic acid decarboxylase (GAD 65), an important putative autoantigen in type 1 diabetes. The NOD background genes strongly influenced antigen processing, that is, different T cell epitopes were generated from the processing of GAD 65 in vivo in the Abeta degree/DQ8 and in the Abeta degree/DQ8/NOD mice.

Sequence organisation of the class II region of the human MHC

We present the genomic organisation of the extended class II region of the human MHC. This initial sequence, which is nearing completion, spans about 1.2 Mbp and is at present a composite of more than one haplotype. The sequencing of single haplotypes is planned for the future. The current sequence encompasses all of the known class II genes at the DP, DO, DM, DQ and DR loci as well as the transporter associated with antigen processing (TAP)/low molecular weight protein (LMP) antigen processing genes and the Tapasin locus, at the extended centromeric end.

Major histocompatibility complex class II polymorphisms in primates

In the past decade, the major histocompatibility complex (MHC) class II region of several primate species has been investigated extensively. Here we will discuss the similarities and differences found in the MHC class II repertoires of primate species including humans, chimpanzees, rhesus macaques, cotton-top tamarins and common marmosets. Such types of comparisons shed light on the evolutionary stability of MHC class II alleles, lineages and loci as well as on the evolutionary origin and biological significance of haplotype configurations.

HLA-DR4 (DRB1*0401) Transgenic Mice Expressing an Altered CD4-Binding Site: Specificity and Magnitude of DR4-Restricted T Cell Response

Optimum function of HLA-DR molecules in transgenic mice requires efficient interaction between the class II molecules on APCs and CD4 on T cells. Residues 110 and 139 of the second domain of class II molecules are considered to be critical for recognition of CD4. We generated an HLA-DR4β(NT) transgene construct in which positions 110 and 139 were altered to resemble endogenous mouse H2 Aβ molecules. This construct was introduced into (B10 × SWR) embryos, and DR4β(NT) transgenic mice were produced. The transgene was transferred into B10.RFB3 (Eβ0 Eαp) mice. The transgene-encoded DR4β molecules paired with endogenous Eα chains to form stable DR4β/Eα dimers expressed on the cell surface. The hybrid dimers showed similar Ag-binding specificity to HLA-DR4 molecules and positively selected CD4+ T cells in vivo. Immunization of HLA-DR4β(NT) transgenic mice with DR4-restricted peptides induced T cell proliferation in vitro. While the purified T cells from DR4β(NT) transgenic mice responded strongly to the HA(307–319) presented by M12C3 transfectants expressing altered DR4β/Eα heterodimers, the response to the same peptides presented by transfectants expressing wild-type DR4β/Eα molecules was substantially reduced. Taken together, these data confirmed in vitro studies on the importance of these residues in CD4-MHC class II interaction. The altered HLA-DR4β transgenic mice were able to overcome the species barrier and generate efficient HLA-DR4-restricted CD4-specific immune responses. Thus, residues 110 and 139 were critical for the interaction of class II with CD4 T cells during thymic selection as well as peripheral immune responses.

A peptide-binding assay for the disease-associated HLA-DQ8 molecule

The study of peptide binding to HLA class II molecules has mostly concentrated on DR molecules. Since many autoimmune diseases show a primary association to particular DQ molecules rather than DR molecules, it is also important to study the peptide-binding properties of DQ molecules. Here we report a biochemical peptide-binding assay for the type I diabetes-associated DQ8, i.e. DQ (alpha1*0301, beta1*0302), molecule. Affinity-purified DQ8 molecules were tested in peptide-binding assays using a radiolabelled influenza haemagglutinin (Ha) peptide encompassing positions 255-271(Y) as an indicator peptide. The Ha 255-271(Y) peptide bound to DQ8 in a pH-dependent fashion showing optimal binding around pH 5. The association kinetics were relatively slow and the resulting complexes were heat labile. The specificity of peptide binding to DQ8 was investigated in competitive inhibition experiments with a panel of 43 peptides of different lengths and sequences. The DQ8 molecules showed a different pattern of peptide binding compared to a previously studied DQ2 molecule. Peptides derived from thyroid peroxidase, HLA-DQ(alpha1*0301), HLA-DQ(alpha1*0302), retinol receptor and p21ras were among the high-affinity binders, whereas peptides derived from myelin basic protein were among the low-affinity binders. The sequence of the high-affinity peptides conformed with a previously published peptide-binding motif of DQ8.

Polymorphism at the HLA-DQ Locus Determines Susceptibility to Experimental Autoimmune Myasthenia Gravis

Studies in myasthenia gravis (MG) patients demonstrate that polymorphism at the HLA-DQ locus influences the development of MG. Several studies using the mouse models also demonstrate the influence of class II molecules, especially the H2-A, which is the mouse homologue of HLA-DQ, in experimental autoimmune myasthenia gravis (EAMG). We used transgenic mice expressing two different DQ molecules, DQ8 (DQA1*0301/B1*0302) and DQ6 (DQA1*0103/B1*0601), to evaluate the role of HLA-DQ genes in MG. These mice do not express endogenous mouse class II molecules since they contain the mutant H2-Aβ0 gene. The mice were immunized with Torpedo acetylcholine receptor, and EAMG was assessed by clinical evaluation and was confirmed by electrophysiology. Clinical scores for EAMG were highest in HLA-DQ8 transgenic mice, whereas the scores of HLA-DQ6 mice rarely exceeded grade 1. There was no incidence of EAMG in class II-deficient (H2-Aβ0) mice. These results demonstrate that polymorphism at the HLA-DQ locus affects the incidence and the severity of EAMG. The manifestation of susceptibility to EAMG in the context of human class II molecules underscores the important roles of these molecules in the initiation and perpetuation of EAMG.

High-resolution HLA typing for the DQB1 gene by sequence-based typing

The ideal high-resolution typing strategy for polymorphic genes is sequence-based typing. SBT of genomic DNA has been developed for the HLA class II genes DRB1, DRB3/4/5 and DPB1. For the DQB1 gene the sequence-based typing method was shown to cause a number of problems. To resolve those problems, different primers to amplify and sequence exon 2 of DQB1 were designed and tested. With several primer combinations, preferential amplification was observed in individuals heterozygous for DQB1*02/*03 and DQB1*02/*04. The preference was for DQB1*02 in many instances but could also be demonstrated for DQB1*03 or *04 and resulted occasionally in allelic drop-out. The best primer combination was selected and successfully used to type individuals heterozygous for DQB1*02, *03 and *04. To distinguish DQB1*0201 and *0202, primers for amplification and sequencing of exon 3 were developed and correct subtyping was obtained. The ambiguous typing DQB1*0301/*0302 and DQB1*0303/*0304 was resolved by allele-specific amplification and sequencing. A total of 258 individuals were fully typed for their DQB1 subtypes. All samples had been previously typed by PCR-SSP and serology. Concordant typing results were obtained for all individuals tested. The DQB1 alleles detected included *0501, *0502, *0503, *0601, *0602, *0603, *0604, *0609, *0201, *0202, *0301, *0302, *0303, *0304, *0401 and *0402. Sequence-based typing of the DQB1 gene proved a reliable typing strategy for assignment of the different DQB1 alleles after intensive selection of primers and test conditions.

T cell recognition of human pre-proinsulin peptides depends on the polymorphism at HLA DQ locus: a study using HLA DQ8 and DQ6 transgenic mice

HLA DQ8 (DQ A1*0301/DQB1*0302) molecule is implicated in the susceptibility to insulin dependent diabetes mellitus whereas, HLA DQ6 (DQ A1*0103/DQB1*0601) molecule may have a protective effect. In this study we used mice transgenic to HLA DQ8 and HLA-DQ6 to elucidate the T cell determinants on a putative islet cell target antigen, insulin. These mice do not express endogenous mouse class II heterodimers on cell surface. Using overlapping synthetic peptides spanning the complete sequence of huma pre-proinsulin, we identified the sequences recognized by T cells in DQ8 transgenic mice and compared these to those in DQ6 transgenic mice. We observed a differential pattern of recognition of epitopes on human pre-proinsulin (HPI) polypeptide presented by the HLA DQ8 allele as compared to HLA DQ6. The sequences 1-24 and 44-63 were immunodominant in DQ8 transgenic mice while DQ6 transgenic mice primarily recognized sequences 14-33 and 74-93 of HPI. We found that the immune response generated in HLA DQ8 transgenic mice against HPI 1-24 cross-reacted to the mouse pre-proinsulin sequence 1-24. The T cell response were specifically inhibited using anti-CD4 and anti-DQ8 monoclonal antibodies. This cross-recognition of self sequences raises the possibility of modulation of experimental diabetes using this peptide.

HLA-DQB1 polymorphism determines incidence, onset, and severity of collagen-induced arthritis in transgenic mice. Implications in human rheumatoid arthritis

Certain HLA-DR alleles have been associated with predisposition to human rheumatoid arthritis (RA). There is also evidence that certain HLA-DQ alleles may also be important in determining susceptibility to RA. We have previously demonstrated that mice transgenic for HLA-DQ8, a DQ allele associated with susceptibility to RA, develop severe arthritis after type II collagen immunization. To investigate the influence of polymorphic difference at the DQ loci on susceptibility to arthritis, we generated mice transgenic for HLA-DQ6, an allele associated with a nonsusceptible haplotype. The DQ6 mice were found to be resistant to collagen-induced arthritis. We also assessed the combined effect of an RA-susceptible and an RA nonassociated DQ allele by producing double-transgenic mice expressing DQ6 and DQ8 molecules, representing the more prevalent condition found in humans where heterozygosity at the DQ allele is common. The double-transgenic mice developed moderate CIA when immunized with CII when compared with the severe arthritis observed in DQ8 transgenic mice, much like RA patients bearing both susceptible and nonsusceptible HLA haplotypes. These studies support a role for HLA-DQ polymorphism in human RA.

Immune response of HLA-DQ8 transgenic mice to peptides from the third hypervariable region of HLA-DRB1 correlates with predisposition to rheumatoid arthritis

The major histocompatibility complex class II genes play an important role in the genetic predisposition to many autoimmune diseases. In the case of rheumatoid arthritis (RA), the human leukocyte antigen (HLA)-DRB1 locus has been implicated in the disease predisposition. The "shared epitope" hypothesis predicts that similar motifs within the third hypervariable (HV3) regions of some HLA-DRB1 alleles are responsible for the class II-associated predisposition to RA. Using a line of transgenic mice expressing the DQB1*0302/DQA1*0301 (DQ8) genes in the absence of endogenous mouse class II molecules, we have analyzed the antigenicity of peptides covering the HV3 regions of RA-associated and nonassociated DRB1 molecules. Our results show that a correlation exists between proliferative response to peptides derived from the HV3 regions of DRB1 chains and nonassociation of the corresponding alleles with RA predisposition. While HV3 peptides derived from nonassociated DRB1 molecules are highly immunogenic in DQ8 transgenic mice, all the HV3 peptides derived from RA-associated DRB1 alleles fail to induce a DQ8-restricted T-cell response. These data suggest that the role of the "shared epitope" in RA predisposition may be through the shaping of the T-cell repertoire.

The human leukocyte antigen TAP2 gene defines the centromeric limit of melanoma susceptibility on chromosome 6p

A single human leukocyte antigen (HLA) class II allele, DQB1*0301, is strongly associated with melanoma, and the HLA-DR locus provides the telomeric boundary for melanoma susceptibility in the HLA class II region of chromosome 6. However, the centromeric boundary is unknown. This study was designed to determine whether the adjacent upstream transporter associated with antigen processing (TAP) locus, TAP2, constitutes the centromeric boundary of disease susceptibility in melanoma. Molecular oligotyping of TAP2 genes was performed for 36 Caucasian patients with melanoma and for 32 Caucasian control individuals by both amplification refractory mutation system (ARMS) polymerase chain reaction (PCR) and PCR-sequence-specific oligonucleotide (SSO) typing. TAP2 allele frequencies in the melanoma patients were compared to those in non-melanoma Caucasian control populations, and to HLA-DQ allele frequencies determined by molecular oligotyping. While HLA-DQB1*0301 was more common in this group of 36 melanoma patients compared to a group of 200 controls (56 percent vs. 27 percent, Bonferoni-corrected chi-square p < = 0.01), no significant differences were observed in TAP2 allele frequencies between melanoma patients and controls. The TAP2 locus represents the centromeric boundary of disease susceptibility for melanoma in the class II region of chromosome 6p. These results support an etiologic role for HLA-DQB1*0301 in melanoma susceptibility.

Expression and function of HLA-DQ8 (DQA1*0301/DQB1*0302) genes in transgenic mice

Transgenic mice expressing HLA-DQA1*0301 and HLA-DQB1*0302 genes (DQ8) were produced. The transgenes were then transferred into mouse (Ab degrees) class II negative mice: the only class II molecules expressed in these animals were therefore coded by the HLA-DQ8 genes. Good expression of HLA-DQ molecules was found. Both CD4+ T cells and DQ8-specific T-cell receptor V beta expressing cells were positively selected in these mice. The HLA-DQ8 molecules expressed in these animals can present various foreign and self antigens and induce T-cell proliferation in vitro. These mice will be invaluable in future studies of the structure and function of HLA-DQ8 genes.

HLA-DQ8 transgenic mice are highly susceptible to collagen-induced arthritis: a novel model for human polyarthritis

Genetic studies have indicated that susceptibility to rheumatoid arthritis (RA) maps to the HLA-DR locus of the major histocompatibility complex. Strong linkage disequilibrium between certain HLA-DQ genes and HLA-DR genes associated with RA, however, suggests that HLA-DQ molecules may also play a role in RA susceptibility. To examine the role of HLA-DQ molecules in arthritis, we generated transgenic mice expressing the DQA1*0301 and DQB1*0302 genes from an RA predisposing haplotype (DQ8/DR4Dw4). The transgenes were introduced into mouse class II-deficient H-2Ab0 mice, and their susceptibility to experimental collagen-induced arthritis was evaluated. The HLA-DQ8+,H-2Ab0 mice displayed good expression of the DQ8 molecule, while no surface expression of endogenous murine class II molecules could be detected. The DQ8 molecule also induced the selection of CD4+ T cells expressing a normal repertoire of V beta T cell receptors. Immunization of HLA-DQ8+,H-2Ab0 mice with bovine type II collagen (CII) induced a strong antibody response that was cross-reactive to homologous mouse CII. Also, in vitro proliferative responses against bovine CII, which were blocked in the presence of an antibody specific for HLA-DQ and mouse CD4, were detected. Finally, a severe polyarthritis developed in a majority of HLA-DQ8+,H-2Ab0 mice, which was indistinguishable from the disease observed in arthritis susceptible B10.T(6R) (H-2Aq) controls. In contrast, HLA-DQ8-,H-2Ab0 fullsibs did not generate CII antibody and were completely resistant to arthritis. Therefore, these results strongly suggest that HLA-DQ8 molecules contribute to genetic susceptibility to arthritis and also establish a novel animal model for the study of human arthritis.

HLA and atopic dermatitis with high serum IgE levels

Patients with atopic dermatitis usually exhibit allergen-specific IgE antibodies against several environmental antigens. HLA restriction is presumed to be involved in the recognition of such antigens, but several previous reports have so far failed to find a significant association between atopic dermatitis and HLA antigens. In this study we examined 38 unrelated Japanese patients with severe atopic dermatitis and high serum IgE levels (greater than 800 U/ml). We investigated the serological HLA types and HLA class II alleles in this group of patients with atopic dermatitis. Frequencies of HLA-A24, A33, Cwblank, B44, DR13 and HLA-DRB1*1302, DQB1*0604, DPB1*0301 alleles were increased in the patients. In contrast, frequencies of HLA-Cw1, Bw6, DR4, DR53, and HLA-DQB1*0302 allele were decreased. However, none of these remained significant after p values were corrected. Further study on HLA association with atopic dermatitis through characterization of specific antigens or antigen epitopes is needed.

MHCDB--database of the human MHC

Genetic and physical data relating to the human major histocompatibility complex (MHC) were compiled and analyzed, using a genome analysis program. The current contents of the database include: 1) location of over 100 genes and other markers; 2) location of over 250 YAC and cosmid clones; 3) 150 kilobases of genomic DNA sequence including full annotation (exon/intron boundaries, repeats, promoters, etc.); 4) cDNA sequences of currently-known class I and class II alleles; and 5) accompanying descriptive data--references, comments, laboratory addresses, and so on. The database allows rapid access, retrieval, and display of all these data, which should make it a useful tool for the study of the human MHC. MHCDB is publicly available and will be updated as new data become available.

Unique intronic variations of HLA-DQ beta gene in early-onset periodontitis

Human leukocyte antigen (HLA) class II beta chain plays an important role in the recognition of foreign antigens in immune reactions. Different forms of immune reaction may be concerned with initiation and progression of infectious diseases such as periodontitis. In this study we examined the frequency of HLA class II serotype and the variation of HLA class II beta gene in periodontitis patients. HLA serotypic frequencies in 70 Japanese patients with periodontitis and 26 individuals with periodontal health were examined. No HLA serotype specific to any type of periodontitis was observed. In order to detect differences among some HLA serotypes, restriction fragment length polymorphism (RFLP) analysis was undertaken with cDNA probes for HLA-DR beta and HLA-DQ beta genes in 20 subjects (15 patients and 5 healthy individuals). Atypical BamHI and EcoRI restriction sites were found in the HLA-DQ beta gene from 3 patients with early-onset periodontitis. In addition to these 20 subjects, an additional 80 subjects (40 patients and 40 healthy individuals) were screened for the atypical BamHI restriction site using the polymerase chain reaction method. It was detected in 7 patients with early-onset periodontitis, 1 patient with adult periodontitis, and 3 healthy subjects. No clinical differences except age were found between patients with this gene variation and other patients. Interestingly, all 3 healthy subjects with this gene variation were from subjects whose family members developed early-onset periodontitis with the gene variation. Atypical BamHI and EcoRI restriction sites and 41-nt repeated sequence were found in the intron before the third exon of HLA-DQB gene. These results suggest that these intronic gene variations may be useful as gene markers for a subpopulation of early-onset periodontitis and might affect immune reactions such as antigen recognition.

RFLP characterization of the upstream regulatory region of the HLA-DQA1 gene

We have performed population and family studies of the distribution of DNA restriction length polymorphisms (RFLPs) in the 5' region of the HLA-DQA1 gene using a probe which corresponds to a sequence of the 5' flanking region of HLA-DQA1. Southern analysis detected four polymorphic fragments (X1, X2, X3 and X4) with XbaI and three fragments (E1, E2 and E3) with EcoRI. Family segregation studies showed that these RFLPs segregated in cis with the parental HLA haplotypes. Analysis of haplotypic associations of the X and E polymorphisms with each other and with HLA-DQA1 alleles demonstrates that DQA1 alleles can be further subtyped according to the particular XE combination which they carry. Hence, definition of these alleles provides new markers for HLA haplotyping and allows further splitting of otherwise identical DQA1 alleles. This information may be helpful for studies of association of disease susceptibility and autoimmunity with HLA haplotypes.

Multi-locus analysis of HLA class II genes in DR2-positive IDDM haplotypes in Finland. The "Childhood Diabetes in Finland" (DiMe) Study Group

In this study we characterized the haplotypes found in IDDM patients that normally confer resistance to the disease in order to localize the polymorphisms relevant for the protection. We studied 15 DR2-positive subjects with IDDM for their DRB1, DRB5 and DQB1 genes using RFLP, polymerase chain reaction (PCR), oligonucleotide typing, and in some specific cases direct sequencing after allele-specific PCR. In addition we analyzed 39 DR2-positive, IDDM non-associated haplotypes representing those haplotypes that are not inherited to probands and hence are present only in healthy family members. The frequency of the DRB1*1501-DRB5*0101-DQB1*0602 haplotype was slightly decreased among diabetic patients (80% vs. 92%). In addition, two unconventional haplotypes DRB1*1501-DRB5*0101-DQB1*05031 and DRB1*1501-DRB5*0101-DQB1*0502 were found in patients with IDDM while all the control ones were conventional. The sequencing of the DQB1*0602 allele present in IDDM haplotypes showed no differences when compared to the controls. These results support the primary but not absolute role of DQ in the protection against IDDM. An additional role of factors centromeric to DQB1 gene was suggested by findings based on the bi-allelic TaqI RFLP polymorphism of the DQA2 gene. All DR2-DQB1*0602 IDDM haplotypes were associated with the 2.1-kb fragment while in the control group the 2.1-kb and 1.9-kb fragments were evenly distributed.

Nucleotide sequencing of HLA-DQ gene second exons in Chinese homozygous cells

Six HLA class I and class II-homozygous Chinese cell lines with unique HLA-Dw types were studied. Since the majority of HLA class II nucleotide sequence polymorphism is localized within the second exons of the genes, we used the polymerase chain reaction (PCR) to amplify these regions in HLA-DQA and DQB genes and subsequently determined the nucleotide sequences. No unique DQA1 or DQB1 alleles were found. However, a new haplotype of DQA1*0601-DQB1*0301-DRB1*1202 was found in two cells; and DQA1*03011 was found in association with DR9 in another two cells. This indicates that new DR-DQ associations may explain the observed new HLA-Dw types. The DQB2 sequences were identical in all six cells and were identical to a sequence previously reported in a DR6 haplotype. The DQA2 sequences from two clones obtained from two cells differed from each other and from previously reported sequences. The results show that the DQA1 and DQB1 alleles in the Chinese individuals studied are as previously reported in Caucasian populations and as such may be typed by restriction fragment-length polymorphism (RFLP) or PCR-sequence-specific oligonucleotide typing (PCR-SSO) or PCR-RFLP using conventional probe or restriction enzyme sets.

Structural similarity of the HLA-DQ region in DQ3 and DQ4 haplotypes and structural diversity of the HLA-DQ region in HLA-DR7 haplotypes

Genomic DNA obtained from a B lymphoblastoid cell line was digested with appropriate restriction endonuclease and hybridized with several probes specific for genes encoding HLA-DQ. Southern hybridization with a DQA1 3'untranslated (UT) region probe showed DQ2-type hybridization pattern in DR7DQ3 haplotype. On the contrary, DQB1 3'UT probe showed DQ3-type pattern in the same haplotype. Gene cloning and DNA sequencing analysis revealed a repetitive sequence, (TG)19, between DQA1 and DQB1 gene in the DR7DQ3 haplotype. These results suggest that a recombination event has occurred near this potential Z-DNA structure in the haplotype, DR7DQ3. The 3'UT region probes of DQA1 and DQB1 genes failed to detect restriction fragment length polymorphism (RFLP) differences between DR4DQ3 and DR4DQ4 haplotypes in this experiment, suggesting that the gene structure between DQA1 and DQB1 is conserved in these haplotypes.

Evolutionary relationships among the primate Mhc-DQA1 and DQA2 alleles

The variation of the Mhc-DQA1 and DQA2 loci of ten different primate species (hominoids and Old World monkeys) was studied in order to obtain an insight in the processes that generate polymorphism of major histocompatibility complex (Mhc) class II genes and to establish the evolutionary relationships of their alleles. To that end nucleotide sequences of 36 Mhc class II DQA1 and seven DQA2 second exons were determined and phylogenetic trees that illustrate their evolutionary relationships were constructed. We demonstrate the existence of four primate Mhc-DQA1 allele lineages, two of which probably existed before the separation of the ancestors of the hominoids and Old World monkeys (approximately 22-28 million years ago). Mhc-DQA2 sequences were found only in the hominoid species and showed little diversity. We found no evidence for a major contribution of recombinational events to the generation of allelic diversity of the primate Mhc-DQA1 locus. Instead, our data suggest that the primate Mhc-DQA1 and DQA2 loci are relatively stable entities that mutated primarily as a result of point mutations.

DNA sequences near a meiotic recombinational breakpoint within the human HLA-DQ region

The molecular organization of HLA-DQ regions derived from DR7, DQw2, and DR4, DQw3 parental haplotypes and DR7, DQw3, a presumed recombinant haplotype, have been studied to define the sequences between DQA1 and DQB1 which may have been involved in this recombinational event. The breakpoint was localized in the intergenic region near the 3' end of the DQB1 gene by restriction mapping. DNA sequences in the immediate vicinity of the breakpoint in DR7, DQw2 (parental), and DR7, DQw3 (recombinant) haplotypes revealed the presence of (CA)22 repeats, minisatellite-related sequences and GC-rich sequences. The intergenic regions varied considerably depending on the haplotype and contained several additional types of repetitive sequences including Alu and LINE repeats. Some of these sequences are related to sequences previously suggested to be involved in meiotic or somatic recombination. In particular, (CA)n repeats, which can adopt the Z-DNA conformation, have previously been shown to promote recombination in several systems.

DNA polymorphisms in the 5'-flanking region of the HLA-DQA1 gene

The HLA-DQA1 gene exhibits haplotype-specific restriction fragment polymorphisms due to DNA rearrangements. We found that some of these polymorphisms extend into the 5' flanking region of the gene and are distinct from other HLA-DQA1 related DNA polymorphisms so far reported. Sequencing of genomic DNA subclones derived from the 5' flanking region of HLA-DQA1 showed the presence, in a DR4 haplotype, of two repetitive elements of the Alu family, oriented in opposite directions and bracketing an approximately 3 kilobase region immediately adjacent to the promoter of the gene. When DNAs extracted from several cell lines were analyzed by genomic hybridization using single-copy probes relative to these intervening sequences, polymorphisms were observed. No structural alterations of the gene immediately outside the DNA portion delimited by the two Alu elements were observed, thus suggesting that polymorphisms of the 5' end of HLA-DQA1 may be limited to the intervening region between the two Alu repeats. The latter includes upstream regulatory elements controlling the expression of the genes. The possibility that the structure of the DNA in this region may influence the regulation of HLA-DQA1 gene expression in different haplotypes is discussed.

Delineation of a previously unrecognized cis-acting element required for HLA class II gene expression

The cis-acting DNA sequences that control expression of the HLA-DPA and HLA-DQB promoters have been investigated in detail. A set of recombinant plasmids containing 5' promoter deletions as well as site-directed mutants of the DPA and DQB genes were fused to a reporter gene and transfected into human B and interferon gamma (IFN-gamma)-inducible cells. A previously unrecognized cis element, which is essential both for transcription induced by IFN-gamma in several cell types and for constitutive class II expression in B cells, in addition to the well known X and Y boxes, has been defined. This sequence, which spans nucleotides -107 to -98 and -146 to -137 of the DPA and DQB promoters, respectively, has been called the J element. Some evidence for function of a fourth element, the S element, is also presented.

Transcription of a subset of human class II major histocompatibility complex genes is regulated by a nucleoprotein complex that contains c-fos or an antigenically related protein

Transcriptional regulation of the human major histocompatibility complex class II genes requires at least two upstream elements, the X and Y boxes, located in the -50- to -150-base-pair region of all class II promoters. The DRA and DPB promoters contain phorbol ester-responsive elements overlapping the 3' side of their X boxes. Mutation of this sequence down-regulates the efficiency of the DRA promoter, suggesting that a positive regulator(s) binds to this site. In this report, anti-sense c-fos RNA and an anti-c-fos antibody were used to show that the product of the protooncogene c-fos or an antigenically related protein is a component of a complex that binds to the X box and is required for maximal transcription from the DRA and DPB promoters. As c-fos (or its related proteins) cannot bind alone to DNA, these results suggest that it may dimerize with other members of the JUN/AP-1 family, such as hXBP1, to participate in the activation of a subset of class II major histocompatibility complex genes.

An isotype-specific trans-acting factor is defective in a mutant B cell line that expresses HLA-DQ, but not -DR or -DP

The B lymphoblastoid cell line clone 13 (a subclone of the mutant cell line P3JHR-1) has been found to express high levels of HLA-DQ; by contrast, HLA-DR and -DP antigens are not expressed and cannot be induced by interferon gamma. Northern blot analysis using gene-specific probes indicated that the lack of surface expression of the DR and DP antigens is due to a marked decrease in the levels of steady-state RNA for both the alpha and beta chains. Southern blots demonstrated that none of the transcriptionally repressed genes are grossly deleted. Preparations of interspecific transient heterokaryons between clone 13 and the class II antigen-positive murine B cell lymphoma, A20, resulted in reactivation of the DRA gene and surface expression of both the DR and DP molecules. The efficiency of the DRA promoter relative to the DQB promoter is markedly and specifically diminished in clone 13 (P3JHR-1) as compared with the parental cell line, Jijoye, as assayed both by transient expression of appropriate chloramphenicol acetyltransferase gene (CAT) constructs and by in vitro transcription analysis. These data clearly demonstrate the existence of an isotype-specific trans-acting factor, and provide direct evidence that the highly homologous class II genes have distinct regulatory mechanisms.

The structure of human MHC class II genes

The class II molecules of the human major histocompatibility complex bind intracellularly processed peptides and present them to T-helper cells. They therefore have a critical role in the initiation of the immune response. A salient feature of the class II molecules is their polymorphism. It has been shown that some autoimmune diseases are associated with certain class II alleles. This article reviews the basic structural features of class II molecules, and the genes encoding them as well as mechanisms governing the development of their extraordinary polymorphism.

Interferon gamma response region in the promoter of the human DPA gene

The interferon gamma (IFN-gamma) response region of the human class II major histocompatibility complex gene, DPA, has been localized to a 52-base-pair (bp) DNA fragment in the proximal promotor at -107 to -55 bp after transfection into HeLa cells of a series of 5', 3', and gap deletion mutants linked to a reporter gene, human growth hormone, as well as of synthetic oligonucleotides fused to the heterologous promoter thymidine kinase. The 52-mer sequence contains the X and Y box elements conserved in all class II genes; their presence is indispensable for IFN-gamma inducibility. Furthermore, an additional 5 bp immediately 5' of the X box of the DPA gene are necessary and sufficient for IFN-gamma induction. This region may contain an IFN-gamma response element. A closely related sequence has also been found in the vicinity of the critical deletion sites of three other well-studied class II gene promoters, all of which require a much longer sequence 5' of the X box. A fourth element, the W element, located about 15 bp 5' of the X box in all class II genes, is clearly of little importance in IFN-gamma inducibility of the DPA gene.

Homologies between the major histocompatibility complex of man and cattle: consequences for disease resistance and susceptibility

The major histocompatibility complex (MHC) of mammals contains a large number of mostly duplicated genes. In the HLA system (the MHC of man), which is by far the best-studied major histocompatibility system so far, roughly 20 genes have been defined and mapped. They code for three classes of proteins: HLA-A, -B and -C (Class I), HLA-DP, -DQ and -DR (Class II) and serum complement components C2, C4 and Bf (Class III). Furthermore, the region contains genes for 21-hydroxylase (21-OH) and tumor necrosis factor (TNF). The MHC thus forms a chromosomal segment containing several clusters of genes of only partially defined biological significance, but ondoubtedly playing a role in disease susceptibility. In view of the recently obtained structural information on BoLA, the MHC of cattle, it is hypothesized that susceptibility to diseases in cattle is associated with BoLA in the same way as human diseases. Finally, new technical and conceptual developments in the field of MHC research and their application to the BoLA system are discussed.

Effect of the AIR-1 locus on the activation of an enhancerless HLA-DQA1 promoter

Studies on the regulation of a major histocompatibility complex (MHC) class II gene, HLA-DQA1, in Ia-positive cells (Raji, a human B-lymphoma cell line) and in isogenic Ia-negative cells (RJ2.2.5, a mutant of Raji altered at the AIR-1 locus) are reported. As previously found, AIR-1 is required in its entirety for the activity of an enhancer factor, the absence of which abolishes transcription of MHC class II genes. In this paper, we show that HLA-DQA1 gene expression can be directed by an enhancerless promoter. The fact that this promoter is inactive in the RJ2.2.5 mutant suggests that the trans-acting element determined by the AIR-1 locus is not only an enhancer factor as previously described, but also acts at the MHC class II promoter level.

A SINE insertion provides information on the divergence of the HLA-DQA1 and HLA-DQA2 genes

The class II region of the human major histocompatibility complex (MHC) contains a cluster of highly polymorphic genes organized into at least three subloci (DR, DQ, and DP), each encoding a subset of surface antigens participating in the modulation of the immune response. Genetic diversity in this system is brought about by two major mechanisms, hypermutation and trans-species evolution. The DQ subregion contains a pair of closely related A genes, HLA-DQA1 and HLA-DQA2, whose phylogenetic relationship is uncertain, although their generation by duplication of an ancestral A gene before or after speciation can be implied. We report here the presence of a member of the Alu repetitive family immediately 5' to the HLA-DQA1 gene. The sequence of this element indicates that it may have integrated by transposition at the time of divergence of hominoids from Old World monkeys. HLA-DQA2 carries an empty integration target site in place of the Alu, thereby suggesting that the insertion of Alu near HLA-DQA1 was preceded by the separation of the two genes.

Applicability of HLA-DQB oligonucleotide typing for the TA10 and 2B3 specificities in routine HLA typing

Our group recently developed oligonucleotide probes associated to the TA10 and 2B3 specificities (1). Unambiguous typings were observed in a panel of homozygous typing cells and a family, using 32P-end labeled probes and PCR-amplified DNA (DQB exon 2). To investigate whether these TA10 and 2B3 associated oligonucleotides could be used in routine HLA-typing we extended the study to a panel of healthy, unrelated individuals. When TA10 and 2B3 typings by oligonucleotides were compared with those obtained in routine serology a complete correlation was observed for TA10. A discrepancy was seen for 2B3 typing in material obtained from DQw5- (and possibly DQw4)-positive individuals which could be explained by the CYNAP (cytotoxicity-negative, absorption-positive) phenomenon, using the IIB3 monoclonal antibody in routine tissue typing. Our results suggest that HLA-DQB oligonucleotide typing for TA10 and 2B3 is an accurate and reliable method and can be used effectively in routine HLA typing.