Direct evidence of homology between human DC-1 antigen and murine I-A molecules

Harnessing Scientific and Technological Advances to Improve Equity in Kidney Allocation Policies

We reported that current assignment of HLA-DQ is a barrier to organ allocation. Here we simulated the impact of incorporating HLA-DQ antigens and antibodies as A/B and αβ allelic variants, respectively, on calculated panel reactive antibody (cPRA) and probability of finding potential compatible donors (PCD). A cohort of 1224 donors and 2075 sensitized candidates was analyzed using HLA-DQαβ allelic (study) versus serologic (current practice) nomenclature. A significant (p < 10^-4 ) decrease in cPRA was observed with higher impact for male versus female, and first transplant versus retransplant (p < 10^-4 ), affecting mostly patients with moderate cPRA (30-80%). Consequently, the number of patients qualifying for 100% cPRA points according to the United Network for Organ Sharing-Kidney Allocation System decreased by 37%. More critically, by using allelic versus serologic nomenclature for HLA-DQ, the number of PCDs for all patients was increased, with male and first-transplant patients showing a higher expansion compared with female and retransplants. Patients of blood group O showed the highest benefit. The goal of reporting unacceptable antigens is to improve accuracy of virtual crossmatching and increase the likelihood of finding immunologically compatible donors. Our simulation provides strong support for the need to re-evaluate the use of allele typing and how HLA-DQ antigens and antibodies are incorporated into allocation policies to ensure equity.

HLA-DQ antibodies: are they real? Are they relevant? Why so many?

PURPOSE OF REVIEW

Recent reports on donor-specific antibodies documented an overwhelming frequency of antibodies to one specific locus - human leukocyte antigen DQ (HLA-DQ). This article provides a short summary of clinical observations, a historic perspective to account for the late recognition of the role of HLA-DQ antibodies as well as potential explanations.

RECENT FINDINGS

The basic understanding of the complexity of HLA-DQ molecules (antigens and antibodies) existed already 3-4 decades ago. However, only more recent advancements in molecular techniques as well as solid phase platforms, that allow for testing antibody specificities against individual HLA targets, provided state-of-the-art tools that are also amenable to mass applications. Thus, the significance of the polymorphic nature of both polypeptide chains of the DQ molecule, DQα and DQβ, is only now re-emerging.

SUMMARY

HLA-DQ antibodies are real, relevant, and abundant. In order to achieve a clinically useful understanding of this phenomenon, HLA-DQ antigens and antibodies should be viewed at the level of the physiologic structure, as it appears on the cell surface, namely, one unit composed as DQαβ. Preliminary data demonstrated that such an approach is likely to lead to more equitable calculation of calculated panel reactive antibody, improving the accuracy of virtual crossmatch prediction, and increasing the likelihood of finding a compatible donor for the very highly sensitized patients.

Th1 epitope peptides induce protective immunity against Rickettsia rickettsii infection in C3H/HeN mice

Rickettsia rickettsii is the causative pathogen of Rocky Mountain spotted fever (RMSF). Adr2, YbgF and OmpB are protective antigens of R. rickettsii. In this study, 90 candidate peptides were selected from these antigens based on their high-affinity binding capacity for the MHC class II molecule H2 I-A or H2 I-E using bioinformatic methods. Six peptides were determined using ELISPOT assay to be immunodominant based on the IFN-γ recall responses of CD4⁺ T cells from mice immunized with R. rickettsii. Six nucleotide sequences encoding the immunodominant peptides were linked in series and inserted into a plasmid for expression in Escherichia coli cells, resulting in a new, recombinant polypeptide termed GWP. After immunization and challenge, the rickettsial load or histopathological lesions in the organs of mice immunized with GWP or pooled peptides was significantly lower than that in organs of mice immunized with PBS or the individual peptide OmpB₃₉₉. An in vitro neutralization test revealed that sera from mice immunized with GWP, OmpB₃₉₉, or pooled peptides reduced R. rickettsii adherence to, and invasion of, vascular endothelial cells. Furthermore, significantly higher levels of IgG, IgG1, or IgG2a were detected in sera from mice immunized with GWP or pooled peptides, and significantly higher levels of IFN-γ or TNF-α secreted by CD4⁺ T cells from R. rickettsii-infected mice were detected after immunization with GWP. Altogether, our results indicated that polypeptides, especially GWP, could induce a Th1-type immune response against R. rickettsii infection, which might contribute to the rational design of peptide-based vaccines for RMSF.

Structural characterization and subcellular localization of Drosophila organic solute carrier partner 1

Background

Organic solute carrier partner 1 (OSCP1) is known to facilitate the transport of various organic solutes into cells and reported to play a role in cell growth and cell differentiation. Moreover, OSCP1 is known as a tumor suppressor gene that is frequently down-expressed in nasopharyngeal carcinomas and acute myeloid leukemia. However, the underlying mechanisms of action remain unclear and the subcellular localization of OSCP1 has yet to be determined in detail.

Results

Drosophila contains a single orthologue of OSCP1 (dOSCP1) that shares 58% homology with its human counterpart. To study the expression pattern and subcellular localization of dOSCP1, we prepared a specific antibody. Subcellular localization analyses of dOSCP1 with these revealed localization in the plasma membrane, endoplasmic reticulum, Golgi apparatus and mitochondria, but no detection in cytosol. dOSCP1 signals were also detected in the nucleus, although at weaker intensity than in plasma membranes and subcellular organelles. In addition, native polyacrylamide gel electrophoresis analysis with and without β-mercaptoethanol treatment revealed that recombinant dOSCP1 forms dimers and trimers in solution. The dimer form of dOSCP1 could also be detected by Western immunoblot analyses in third instar larval extracts.

Conclusions

The data revealed that dOSCP1 localizes not only in the plasma membrane but also in the nucleus, ER, Golgi apparatus and mitochondria. It is therefore conceivable that this protein may interact with various partners or form multimeric complexes with other proteins to play multiple roles in cells, providing clues to understanding the functions of dOSCP1 during Drosophila development.

Prediction and characterization of helper T-cell epitopes from pneumococcal surface adhesin A

Pneumococcal surface adhesin A (PsaA) is a multifunctional lipoprotein known to bind nasopharyngeal epithelial cells, and is significantly involved in bacterial adherence and virulence. Identification of PsaA peptides that optimally bind human leucocyte antigen (HLA) and elicit a potent immune response would be of great importance to vaccine development. However, this is hindered by the multitude of HLA polymorphisms in humans. To identify the conserved immunodominant epitopes, we used an experimental dataset of 28 PsaA synthetic peptides and in silico methods to predict specific peptide-binding to HLA and murine MHC class II molecules. We also characterized spleen and cervical lymph node (CLN) -derived T helper (Th) lymphocyte cytokine responses to these peptides after Streptococcus pneumoniae strain EF3030 challenge in mice. Individual, yet overlapping, peptides 15 amino acids in length revealed residues of PsaA that consistently caused the highest interferon-γ, interleukin-2 (IL-2), IL-5 and IL-17 responses and proliferation as well as moderate IL-10 and IL-4 responses by ex vivo re-stimulated splenic and CLN CD4⁺ T cells isolated from S. pneumoniae strain EF3030-challenged F1 (B6 × BALB/c) mice. In silico analysis revealed that peptides from PsaA may interact with a broad range of HLA-DP, -DQ and -DR alleles, due in part to regions lacking β-turns and asparagine endopeptidase sites. These data suggest that Th cell peptides (7, 19, 20, 22, 23 and 24) screened for secondary structures and MHC class II peptide-binding affinities can elicit T helper cytokine and proliferative responses to PsaA peptides.

Helper T cell epitope-mapping reveals MHC-peptide binding affinities that correlate with T helper cell responses to pneumococcal surface protein A

Understanding the requirements for protection against pneumococcal carriage and pneumonia will greatly benefit efforts in controlling these diseases. Several proteins and polysaccharide capsule have recently been implicated in the virulence of and protective immunity against Streptococcus pneumonia. Pneumococcal surface protein A (PspA) is highly conserved among S. pneumonia strains, inhibits complement activation, binds lactoferrin, elicits protective systemic immunity against pneumococcal infection, and is necessary for full pneumococcal virulence. Identification of PspA peptides that optimally bind human leukocyte antigen (HLA) would greatly contribute to global vaccine efforts, but this is hindered by the multitude of HLA polymorphisms. Here, we have used an experimental data set of 54 PspA peptides and in silico methods to predict peptide binding to HLA and murine major histocompatibility complex (MHC) class II. We also characterized spleen- and cervical lymph node (CLN)-derived helper T lymphocyte (HTL) cytokine responses to these peptides after S. pneumonia strain EF3030-challenge in mice. Individual, yet overlapping peptides, 15 amino acids in length revealed residues 199 to 246 of PspA (PspA_199–246) consistently caused the greatest IFN-γ, IL-2, IL-5 and proliferation as well as moderate IL-10 and IL-4 responses by ex vivo stimulated splenic and CLN CD4⁺ T cells isolated from S. pneumonia strain EF3030-challeged F₁ (B6×BALB/c) mice. IEDB, RANKPEP, SVMHC, MHCPred, and SYFPEITHI in silico analysis tools revealed peptides in PspA_199–246 also interact with a broad range of HLA-DR, -DQ, and -DP allelles. These data suggest that predicted MHC class II-peptide binding affinities do not always correlate with T helper (Th) cytokine or proliferative responses to PspA peptides, but when used together with in vivo validation can be a useful tool to choose candidate pneumococcal HTL epitopes.

Dynamic changes in the subcellular localization of Drosophila beta-sarcoglycan during the cell cycle

One of the proposed roles of sarcoglycan is to stabilize dystrophin glycoprotein complexes in muscle sarcolemma. Involvement in signal transduction has also been proposed and abnormalities in some sarcoglycan genes are known to be responsible for muscular dystrophy. While characterization of sarcoglycans in muscle has been performed, little is known about its functions in the non-muscle tissues in which mammalian sarcoglycans are expressed. Here, we investigated temporal and spatial expression patterns of Drosophila beta-sarcoglycan (dScgbeta) during development by immunohistochemistry. In addition to almost ubiquitous expression in various tissues and organs, as seen for its mammalian counterpart, anti-dScgbeta staining data of embryos, eye imaginal discs, and salivary glands demonstrated cytoplasmic localization during S phase in addition to plasma membrane staining. Furthermore we found that subcellular localization of dScgbeta dramatically changes during mitosis through possible association with tubulin. These observations point to a complex role of sarcoglycans in non-muscle tissues.

Complete sequence of an HLA-dR beta chain deduced from a cDNA clone and identification of multiple non-allelic DR beta chain genes

At least three polymorphic class II antigens are encoded in the human major histocompatibility complex (HLA): DR, DC and SB. cDNA clones encoding beta chains of HLA-DR antigen, derived from mRNA of a heterozygous B-cell line, were isolated and could be divided into four subsets, clearly distinct from cDNA clones encoding DC beta chains. Therefore, at least two non-allelic DR beta chain genes exist. The complete sequence of one of the DR beta chain cDNA clones is presented. It defines a putative signal sequence, two extracellular domains, a trans-membrane region and a cytoplasmic tail. Comparison with a DC beta chain cDNA clone revealed a homology of 70% between the two beta chains and that the two genes diverged under relatively little selective pressure. A set of amino acids conserved in immunoglobulin molecules was found to be identical in both DR and DC beta chains. Comparison of the DR beta chain sequence with the amino acid sequence of another DR beta chain revealed a homology of 87% and that most differences are single amino acid substitutions. Allelic polymorphism in DR beta chains has probably not arisen by changes in long blocks of sequence.

Distinct subsets of stromal cells confined to unique microenvironments in human endometrium throughout the menstrual cycle

Human endometrial stroma exhibits rather uniform morphology throughout the endometrium. However, predecidualization develops characteristically around vessels and subsequently around glands and under surface epithelium, demonstrating existence of regional differences among stromal cells. Immunoreactivity of stromal cells in endometrial tissues from various phases of the menstrual cycle, as elucidated by employing monoclonal antibodies to cytokeratin, vimentin, very late antigen-1 (VLA-1), Ber-EP4, and HLA-DR, revealed presence of phenotypically distinct subsets of stromal cells confined to unique microenvironments throughout the menstrual cycle. All stromal cells strongly expressed vimentin and weakly expressed cytokeratin. However, Ber-EP4 positive stromal cells were distinctly confined around glands and to the subluminal regions of the surface epithelium. The intervening stromal cells were Ber-EP4 negative. The HLA-DR positive stromal cells were characteristically present in three different locations: around glands and under surface epithelium, around blood vessels and around HLA-DR positive lymphoid cells. From all antigens studied, only expression of VLA-1 in the stromal cells showed a characteristic change throughout the menstrual cycle. Stromal cells in the proliferative and early secretory phases were VLA-1 negative. However, VLA-1 characteristically developed initially in the HLA-DR positive cells around vessels and then in HLA-DR/Ber-EP4 positive cells around glands and under surface epithelium. Eventually, all stromal cells in the upper functionalis expressed VLA-1 in the late secretory phase of the menstrual cycle. These data underscore a heterogeneity in stromal cells not exemplified by their morphology. Also, they provide a basis for understanding the differences that the stroma exhibits in morphologic and functional differentiation throughout the menstrual cycle.

Human chromosome 16 encodes a factor involved in induction of class II major histocompatibility antigens by interferon gamma

Interferon gamma (IFN-gamma) induces expression of class II major histocompatibility complex (MHC)-encoded antigens in immunocompetent cells. To gain further insight into the mechanism of this induction, we prepared somatic cell hybrids between different human cell lines and a murine cell line, RAG, that does not express murine class II MHC antigens before or after treatment with murine IFN-gamma. Some of the resulting cell hybrids express murine class II MHC antigens when treated with murine IFN-gamma. This inducible phenotype is correlated with the presence of human chromosome 16. It has been shown previously that the induction of class I MHC antigens by human IFN-gamma in human-rodent hybrids requires the presence of species-specific factors encoded by chromosome 6, which bears the gene for the human IFN-gamma receptor, and chromosome 21, whose product(s) is necessary for the transduction of human IFN-gamma signals. In this report, we show that the induction of murine class II MHC antigens by human IFN-gamma in the human-RAG cell hybrids requires, likewise, the presence of human chromosomes 6 and 21, in addition to chromosome 16. In some of these hybrids, when all three of these human chromosomes were present, induction of cell-surface HLA-DR antigens was also observed. Our results demonstrate that human chromosome 16 encodes a non-species-specific factor involved in the induction of class II MHC antigens by IFN-gamma.

Human endometrial epithelial cell lines for studying steroid and cytokine actions

Recent studies suggest that the proliferation and expression of HLA-DR molecules in endometrial epithelium may be regulated by systemic steroids and local cytokines. To test the interacting influences of cytokines and steroids on the expression of HLA-DR and proliferation of epithelial cells, an endometrial cell model is required that is sensitive to both signals. In this study, we characterize cells of carcinoma cell lines of endometrial lineage for their responsiveness to cytokines and steroids. Independently developed for its response to steroid hormones from a well-differentiated adenocarcinoma of human endometrium, EnCa101AE cell line is further cloned for the expression of progesterone receptor. Immunohistochemical localization using monoclonal antibodies demonstrates that both EnCa101AE cell line and cloned ECC1 cells are purely epithelial, as evidenced by the expression of cytokeratin and epithelial membrane antigen, express estrogen receptors, and concomitantly exhibit IFN-gamma receptor. Experiments using radioiodinated IL-1 reveal that these cell lines also possess high affinity receptors for IL-1. As indicated by the induction of HLA-DR molecules, and alterations in morphologic characteristics, these cell lines are sensitive to both IFN-gamma and IL-1 action. The class II molecules (HLA-DR, HLA-DP, and HLA-DQ) are differentially induced by IFN-gamma treatment in carcinoma cell lines, with HLA-DR being the prevailing induced molecule. IFN-gamma inhibits and estradiol-17 beta promotes growth of ECC1 cells in a dose- and time-dependent manner. These findings indicate that the interacting effect(s) of the cytokines and steroid hormones on endometrial epithelium may be studied in these unique steroid- and cytokine-sensitive epithelial cell lines.

T-cell subsets in healthy teenagers: transition to the adult phenotype

Little is known about the normal range and variability of T-cell subsets in older children. We analyzed peripheral blood mononuclear cell subsets in 112 healthy children, ages 12-19 years (mean +/- SD: 15.4 +/- 1.9 years), using monoclonal antibodies and flow cytometry. The study population included 28 blacks and 84 whites, with 59 boys and 53 girls. The mean +/- SD cell subset values were: CD3+ T cells, 74.0 +/- 7.8%; CD4+ helper-inducer T cells, 46.8 +/- 6.9%; CD8+ suppressor-cytotoxic T cells, 27.3 +/- 5.7%; CD4:CD8 helper:suppressor ratio, 1.81 +/- 0.57; CD16+ natural killer cells, 4.4 +/- 3.1%; CD19+ B cells, 10.0 +/- 5.3%; CD14+ monocytes, 20.0 +/- 6.5%; and HLA-DR cells, 15.4 +/- 4.8%. Overall, boys had a higher proportion of HLA-DR+ cells than girls, attributable to an increase in CD19+ B cells. Blacks tended to have a higher proportion of HLA-DR+ cells than whites, apparently due to an increase in activated T cells. Detailed analysis by age group revealed a striking transition in the pattern of CD4+ and CD8+ cell populations. The CD4:CD8 ratio, higher in boys than girls for ages 12-16, was reversed to the "adult" pattern in 17-19 year olds, with a higher CD4:CD8 ratio in girls. These data provide important baseline values for healthy children and stress the importance of establishing normative ranges for pediatric subjects separately from adults.

The effects of cigarette smoking on T cell subsets. A population-based survey of healthy caucasians

To investigate the influence of cigarette smoking on mononuclear cell subsets, we determined T cell, B cell, monocyte, and HLA-DR+ subsets in a population-based, stratified, random sample of healthy Caucasians using monoclonal antibodies and flow cytometry. The study population consisted of 282 subjects 20 to 69 yr of age, including 108 smokers and 174 nonsmokers. Multivariate analysis techniques were used to assess the influence of cigarette smoking status after controlling for the effects of age and gender. Cigarette smoking was associated with a nonspecific increase in the leukocyte count involving all major cell types (smokers: 8.50 +/- 0.15 versus nonsmokers: 7.33 +/- 0.12 cells/mm3; p less than or equal to 0.0001). In addition, cigarette smokers had a selective increase in CD4+ cells (helper-inducer T cells) compared with nonsmokers (55.3 +/- 0.8 versus 52.2 +/- 0.6% of lymphoid cells; p = 0.002), resulting in a statistically significant increase in the CD4+/CD8+ (helper/suppressor) ratio (2.42 +/- 0.1 versus 2.13 +/- 0.16; p = 0.02). There was no significant difference between smokers and nonsmokers in the level of CD3+ cells (total T cells: 76.8 +/- 0.7 versus 76.1 +/- 0.5; p = 0.5), CD8+ cells (suppressor-cytotoxic T cells: 25.7 +/- 0.8 versus 27.0 +/- 0.5%; p = 0.1), CD19+ cells (B cells) (10.7 +/- 0.4 versus 10.0 +/- 0.3%; p = 0.2), CD14+ cells (monocytes) (18.0 +/- 0.6 versus 17.0 +/- 0.4%; p = 0.2), or HLA-DR+ cells (14.5 +/- 0.5 versus 14.0 +/- 0.4%; p = 0.4).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of age, race, and gender on peripheral blood mononuclear-cell subsets in healthy nonsmokers

To investigate the influence of age, race, and gender on the cellular immune system, we determined T-cell, B-cell, monocyte, natural killer (NK)-cell, and HLA-DR+-cell subsets in 266 nonsmokers from a population-based random sample of healthy adults using monoclonal antibodies and flow cytometry. Blacks had a lower total white blood-cell count than whites (P less than or equal to 0.0001), due primarily to a decrease in granulocytes. There was no significant difference in absolute lymphocyte count between blacks and whites. Blacks had a higher proportion of CD19+ cells (Leu 12+ B cells) and a lower proportion of CD3+ cells (OKT3+ T cells) than whites (P less than or equal to 0.01). Female sex and increasing age were independently associated with an increased percentage of CD4+ cells (OKT4A+ helper-inducer T-cell subset), resulting in a higher helper/suppressor ratio among women and older individuals (P less than or equal to 0.05). Black race and increasing age were independently associated with an increased proportion of HLA-DR+ cells (P less than or equal to 0.0001) which was not attributable to B cells or monocytes. No significant age, race, or gender effects were observed for CD14+ cells (Leu M3+ monocytes) or CD16+ cells (Leu 11A+ natural killer cells). These data demonstrate that age, race, and gender are each associated with significant differences in peripheral blood mononuclear-cell subsets. Population-based data such as these provide an important foundation for future design and interpretation of human flow cytometry data.

T-cell identification of a private DQw5 subtype associated with DR1: contribution of endogenous peptide?

Human allospecific T-cell clones were generated against DR1 and DQw1 by limiting dilution. In proliferation experiments using a large panel of Epstein-Barr virus-transformed B-cell lines (LCL), eight T-cell clones (TLC) were found that responded only to the DR1+ LCLs* (9 of 9) and not the 94 other LCLs expressing DR specificities 2 through w9. TLCs* were analyzed further using monoclonal antibodies in blocking studies. As expected, most TLCs were blocked by anti-DR monoclonal antibodies (MoAbs)* and not by anti-DQ MoAbs. However, one clone, TLC 63.138, was not blocked by anti-DR MoAbs but was completely inhibited by anti-DQ MoAbs. This suggests that TLC 63.138 recognizes a private determinant on DQ molecules uniquely associated with DR1.

T lymphocyte clones recognizing an HLA-DQw3.2-associated epitope involving residue 57 on the DQ beta chain

The DQw3.2 specificity has previously been recognized using genomic RFLP analysis and certain combinations of monoclonal antibodies. Here we report three CD4+ T lymphocyte clones (TLCs) generated from a DR3,4; DQw2,w3.1 responder stimulated with cells from a DR3,4; DQw2,w3.2 donor, and using a modified cloning procedure involving enrichment of IL-2 receptor-positive T cell during priming. The resulting TLCs were strongly inhibited by some monoclonal anti-DQ, but not anti-DR or -DP antibodies. In panel studies using HLA homozygous stimulating cells, it was found that the TLCs recognize an HLA epitope encoded by a DQ gene carried only by DR4,DQw3.2 haplotypes. By comparison with published DQ chain amino acid sequences of some stimulating cells able or not to induce a response in these clones, evidence was obtained that Ala at position 57 on the DQ beta chain is most probably involved in the epitope. The epitope is present on cells from 12 out of 12 DR4,DQw3 insulin dependent diabetes mellitus (IDDM) patients, but on cells only from 6 out of 12 healthy DR4,DQw3 controls. Thus, a DQ-encoded epitope involving residue 57 on the DQ beta chain, and which is strongly associated to IDDM, may be recognized by T cells.

A specific nucleotide sequence defines a functional T-cell recognition epitope shared by diverse HLA-DR specificities

An oligonucleotide probe that distinguishes the HLA-DR4, Dw14 allele from other HLA-DR4-associated class II genes was used to identify a common nucleotide sequence shared between the DR beta 1 locus encoding HLA-DR1 (Dw1), Dw16, and DRw10 haplotypes. The presence of this nucleotide sequence correlated with the ability of these haplotypes to stimulate an alloreactive proliferative T-cell clone (clone 14B) raised against a Dw14+ stimulator cell. Alleles of DR beta 1 that differ by one specific nucleotide variation at codon 71 neither hybridize to the Dw14-specific oligonucleotide nor stimulate clone 14B. These data demonstrate the presence of a shared epitope present on serologically distinct DR alleles that is recognized as a specific allodeterminant by a single T-cell clone.

DQw3 variants defined by cloned alloreactive T cells

The polymorphism of HLA class II molecules expressing the serologically defined alloantigen DQw3 was studied using cloned proliferative T lymphocytes. Two clones, IG9 and IC3, were selectively primed against DQw3-associated determinants and tested against a panel of 92 HLA-D homozygous cells. Both clones were specific for DQw3, but each showed a distinct response pattern. Clone IG9 recognized a DQw3-associated determinant expressed on a subset of DR4 and DR5 haplotypes and on all DRw6, 7, w8, and w9 haplotypes tested. In contrast, clone IC3 recognized a distinct DQw3-associated determinant expressed only on a subset of DR4 haplotypes. In monoclonal antibody inhibition experiments, anti-DQ, but not anti-DR or anti-DP antibodies, blocked reactivity of both clones IG9 and IC3, further demonstrating that the determinants defined by these clones are associated with DQ molecules. In DNA hybridization studies using a DQ beta probe, a correlation was observed between restriction site polymorphisms in the DQ beta gene, designated DQw"3.1" and "3.2," and the expression of the T-cell-defined IG9 and IC3 determinants. It is, thus, possible to demonstrate by cloned T-cell reactivity functionally relevant recognition sites on DQw3+ molecules that are associated with structural polymorphisms defined by molecular and genomic analysis.

Simultaneous cytometric analysis for the expression of cytoplasmic and surface antigens in activated T cells

A method of two-colour immunofluorescence staining has been developed to allow the simultaneous analysis of both surface and cytoplasmic antigens. This involves the use of direct fluorochrome antibody conjugates for cell-surface antigen staining, followed by cell permeabilization and the staining of cytoplasmic antigens with biotinylated antibodies and streptavidin-fluorochrome conjugates. Fluorochrome-antibody conjugates bound to cell-surface epitopes were found not to be affected by the subsequent permeabilisation and cytoplasmic staining. This method was used to examine the surface phenotype of T cells expressing a cytoplasmic antigen, STA. STA is a unique determinant detected in activated human T cells by the monoclonal antibody K-1-21, which also recognizes a cross-reactive conformation-dependent epitope on human free kappa light chains. Cytometric analysis showed that STA is found in both Leu 2a+ cytotoxic/suppressor T cells and Leu 3a+ helper/inducer T cells but is not induced in the Leu 15+ population which contains suppressor T cells. STA was also shown to be an activation antigen in murine T cells.

Molecular genotyping of the HLA-DQ alpha gene region

Restriction fragment analysis has been applied to genomic DNA extracted from human tumor cell lines. Polymorphic restriction fragments encompassing the HLA-DQ alpha gene were observed upon digestion with Bgl II, Eco RI, and Hind III. Analysis of these polymorphic fragments (or allogenotopes) showed that for each restriction enzyme a series of three differently sized allogenotopes existed. Clusters of cosegregating allogenotopes belonging to the different allelic series defined three different allogenotypes. Each allogenotype exhibited a distinctive restriction map generated by digestion with five restriction enzymes. Comparison of these restriction maps showed that generation of the polymorphisms observed at the HLA-DQ alpha region in these sets of cell lines is not caused by a single event. In some B- and T-lymphoma cell lines a fourth allogenotype was found. The restriction site map of genomic DNA from these cell lines suggested that the latter distribution of restriction enzyme sites was most probably generated by recombination between two of the previously observed allogenotypes at a crossover site(s) adjacent to the HLA-DQ alpha gene.

A novel human class II specificity, DQ "Wa," resides on DQ molecules of DR4,Dw15 and DRw8,Dw8 B-cell lines identified as DQ "blank"

The molecular localization of a novel human class II specificity, DQ "Wa," was investigated. A monoclonal antibody, HU46, which has previously been shown to react with DR4, Dw15 and DRw8, Dw8 B cells that type as DQ "blank," was used for the isolation and structural characterization of class II molecules bearing the DQ "Wa" determinant. The partial N-terminal sequence analysis of class II molecules bearing the DQ "Wa" determinant, purified from two B-cell lines, EBV-Wa (DR4, Dw15, DQ "blank") and GI (DRw8, Dw8, DQ "blank"), shows that the alpha and beta chain sequences are homologous to HLA-DQ. Within the limits of our analysis, the alpha and beta chains from both cell lines are identical. Both beta chains possess a phenylalanine residue at position 9 that differs from the tyrosine residue present at this position in beta chains of DQ alleles. These studies indicate that a novel human class II specificity, DQ "Wa," resides on a new allelic form of DQ molecules found in DR4, Dw15 and DRw8, Dw8 cells that are DQ "blank."

Detection of a novel HLA-DQ specificity: serological and immunochemical analyses by a monoclonal antibody

A monoclonal antibody (mAb) with a novel human B-cell allospecificity was produced by immunizing a C3H/He mouse with the human B lymphoblastoid cell line EBV-Wa (HLA-DR4/Dw15/DQblank homozygous). The mAb, termed HU-46, reacted with B cells from not only DR4/Dw15-positive individuals but also certain DRw8/Dw8-positive ones whose DQ phenotypes had not yet been defined. Two-dimensional gel analyses indicated that the mAb recognized class II antigens which were encoded by the HLA-DQ locus. Furthermore, in genetic analysis, the gene encoding the class II antigen detected by HU-46 met the Hardy-Weinberg condition as a fourth allele of the DQ locus. We provisionally labeled this novel DQ specificity DQWa.

The development and analysis of species specific and cross reactive monoclonal antibodies to leukocyte differentiation antigens and antigens of the major histocompatibility complex for use in the study of the immune system in cattle and other species

We examined the potential of developing a set of species specific and cross reactive monoclonal antibodies (MoAbs) for use in the study of the phylogenetic and functional relation of class I and class II antigens of the major histocompatibility complex (MHC) and leukocyte differentiation antigens in cattle and other species. Comparing immunization strategies demonstrated the number of hybrids producing cross reactive antibodies can be increased by hyperimmunization of mice with lymphoid cells from multiple species. Comparing various methods of assay (antibody-complement mediated cytotoxicity [CT], enzyme linked immunosorbent assay [ELISA] and flow microfluorimetry [FMF]), revealed FMF is the most useful technique for the primary assay of hybridomas producing MoAbs of potential interest. By using dual parameter and dual fluorescence analysis, we could determine whether a given MoAb reacted with mononuclear cells (lymphocytes and monocytes) and/or granulocytes, and also whether any two MoAbs of different isotype and specificity recognized antigens present on identical or separate populations of leukocytes. Comparing the patterns of MoAb reactivity with leukocytes obtained from cows, goats, sheep, pigs, horses and humans, as well as comparing the patterns of reactivity with a panel of lymphoid cell lines derived from cattle (with enzootic bovine leukemia) and humans (with various forms of leukemia), revealed sets of MoAbs reactive with unique antigenic determinants present on BoLA class I (15 MoAbs) and class II (9 MoAbs) antigens, and also MoAbs reactive with determinants present on leukocyte differentiation antigens (36 MoAbs). Dual fluorescence analysis demonstrated the antigens detected by some MoAbs are predominantly expressed on one lineage of leukocytes while others are expressed on two or more lineages of leukocytes. Dual and single fluorescence analysis also demonstrated the PNA receptor(s) is: expressed on T cells, granulocytes and class II antigen monocytes and absent or expressed in low amount on sIgM+ B cells and a newly defined Non T/Non B population of cells. The strategies described for identifying and analyzing the specificity of MoAbs demonstrate the feasibility of developing a set of cross reactive MoAbs for identifying homologous molecules in multiple species and delineating their functional and phylogenetic relation.

Expression of HPCA-1 and HLA-DR antigens on growth factor- and stroma-dependent colony forming cells

The expression of HLA-DR and HPCA-1 antigens (recognized by the L243 and BI.3C5 antibodies respectively) on adult human bone marrow cells was examined by fluorescence activated cell sorting and colony assays. Nearly all the (day 14) lineage restricted and multipotential colony forming cells analysed in methylcellulose cultures in the presence of added growth factors express HLA-DR and HPCA-1 determinants. Two colour cell sorting reveals that the lineage restricted HLA-DR positive progenitors express variable levels of BI.3C5 positivity whereas most of the multipotential progenitors, the multi-CFC or CFU-GEMM, are highly BI.3C5 positive. The isolated HLA-DR and BI.3C5 positive populations also contain haemopoietic precursors which adhere to and form colonies on pre-formed stromal layers. Thus, haemopoietic progenitors assayed in both types of culture system can be analysed and enriched by simultaneous two-colour sorting using anti-HLA-DR and BI.3C5 monoclonal antibodies. Similarities in the antigenic phenotype of such cells, however, precludes the use of these reagents for segregating growth factor-dependent from stroma-dependent progenitors.

Monoclonal antibodies that distinguish between class II antigens (HLA-DP, DQ, and DR) in 14 haplotypes

The specificity of three commonly used monoclonal antibodies (MoAbs) reacting with human class II histocompatibility antigens, was analyzed to determine whether these MoAbs would distinguish between HLA-DP, DQ, and DR in a large number of haplotypes. The reactivity of these MoAbs (L243, Anti-Leu 10, and B7/21) was compared by serial immunoprecipitation of class II antigens from 11 B-cell lines. The cell lines examined expressed a total of five DP, three DQ, and nine DR types, which together represent most of the well-defined class II specificities. This is the first demonstration that one of these antibodies, B7/21. binds to at least five DP specificities, and does not bind to DR or DQ molecules as defined by reactivity with the two other MoAbs. Within the scope of these experiments, the B7/21 antibody was shown to react with a monomorphic DP determinant. A variant clone of the B7/21 hybridoma was isolated that secretes IgG1 antibody with the same specificity as the original IgG3 antibody. The two other antibodies studied have been previously shown to react with DR molecules (L243) or DQ molecules (Anti-Leu 10). Here, their lack of cross-reaction with DP molecules is demonstrated. Thus, each of the three MoAbs reacts exclusively with a distinct class II molecule in all haplotypes studied, and therefore should be useful for comparing the independent expression and function of DP, DQ, and DR molecules.

Expression of HLA class II determinants by normal and chronic myeloid leukemia progenitors

It has been suggested that the expression of some HLA class II antigens, derived from three loci (DR, DP, DQ) is important in the regulation of both the immune response and the response of haemopoietic progenitors to regulation factors, such as acidic isoferritins (AIF), as well as in the interaction between T lymphocytes and erythroid progenitors (BFU-E). Changes in the expression of class II antigens have been reported on the surface of granulo-monocyte progenitors in chronic myeloid leukemia (CML) and correlated to the abnormal proliferation of such cells. In this study, monoclonal antibodies against DR and DQ monomorphic determinants were used to investigate the expression of these antigens on the surface of normal and CML bone marrow and peripheral blood BFU-E by means of complement mediated cytotoxicity. It was found that most normal and leukemic BFU-E express DR antigens. Antigens density tends to be greater on marrow as opposed to peripheral precursors. In addition, leukemic BFU-E are more sensitive to cytolytic treatment than their normal counterparts. Normal BFU-E do not express detectable amounts of DQ antigens, whereas these are present on a proportion of leukemic BFU-E.

Immunochemically purified DR antigens in liposomes stimulate xenogeneic cytolytic T cells in secondary in vitro cultures

A monoclonal antibody directed against the human class II major histocompatibility antigen DR was generated. Use of this antibody, LB3.1, allowed isolation of large amounts of highly purified DR by immunoaffinity chromatography. The DR was reconstituted into liposomes and shown to stimulate secondary xenogeneic cytolytic T lymphocytes (CTL) specific for targets expressing DR antigens. DR digested with neuraminidase was equally as effective as native DR at stimulating CTL, while denatured DR and other purified membrane proteins were much less effective. The DR liposome-induced CTL lysed only target cells expressing class II antigens. Cytolysis of targets bearing class II antigens was blocked by DR-specific antisera.

Characterization of a monoclonal antibody recognizing a monomorphic determinant of the alpha chain of class II DQ antigens

We have characterized a monoclonal antibody (L2) specific for a determinant of Human DQ class II antigens. After immunoprecipitation and immunofluorescence analysis performed on a panel of DR homozygous cell lines and HLA deleted mutants, it behaves like a monomorphic anti-DQ reagent and does not react with the products of the various DR alleles. On immunoblotting, it reacts with an epitope of the DQ alpha chain.

Functional characterization of infiltrating T lymphocytes in human hepatic allografts

We have employed recently developed techniques in T-cell culturing to study the nature and function of infiltrating hepatic allograft T cells. Using the rationale that intragraft T cells are activated during cell mediated damage to the allograft, we were able to show that these cells would propagate and remain functionally active in the presence of the T-cell growth factor, IL-2. In several instances, phenotypic analysis of cells grown in this manner was very similar to that found within the graft. Both proliferative and cytotoxic responses could be detected from the cultured cell lines. The majority of the proliferative responses were donor-directed and immunogenetic analysis could define donor-directed HLA reactivity, to either class I or class II antigens, or both. Monoclonal anti-HLA antibodies inhibition profiles verified the apparent HLA reactivity. In a smaller percentage of cases, only IL-2 responsiveness could be detected, and no HLA reactivity could be determined. Cytotoxicity could be detected against both class I and class II antigens, however, those cells which demonstrated a greater magnitude of donor-directed cytotoxicity appeared to be directed against class I antigens. A significant correlation between donor-directed proliferation of biopsy cultured lymphocytes and cellular rejection was found. This model appears to be useful in delineating functions of the intragraft T-cell population during rejection.

A biochemical characterization of feline MHC products: unusually high expression of class II antigens on peripheral blood lymphocytes

The polymorphism of feline MHC antigens was examined using biochemical methods. The following observations were made: (1) feline class I and II antigens are polymorphic. Their biochemical features were established using rabbit and mouse reagents directed against human MHC products; they resemble those observed for other mammalian species; (2) the expression of class II antigens in unstimulated cat peripheral blood lymphocytes (PBLs) appears to be unusually high. Cat PBLs express far more class II than class I antigens, whereas in human Epstein-Barr virus-transformed lines, which are known to express relatively large amounts of class II antigens, the situation is reversed.

Imbalanced MHC class II molecule expression at surface of murine B cell lymphomas

To study the role of class II MHC expression in mouse lymphomagenesis, we examined the cell surface expression of I-A/E antigens on 24 spontaneous or murine leukemia virus (MuLV)-induced mouse B10.A (I-Ak, I-Ek) B cell lymphomas. Two primary B10.A B cell lymphomas were observed with strong I-Ek expression but with only minimal cell surface I-Ak expression. Both tumors are readily transplantable in syngeneic mice, with maintenance of their I-A-, I-E+ phenotype. Strikingly, one I-A-, I-E+ B cell lymphoma contains a (11; 17) translocation with a breakpoint on chromosome 17 that is localized within or very close to the H-2 complex. DNA of both tumors contains normal restriction enzyme fragments of the A alpha and A beta genes. Northern blot analyses indicated that one I-A-, I-E+ tumor strongly expressed A alpha, E alpha, and E beta mRNAs but possessed only a weak expression of A beta mRNA. The other B cell lymphoma showed A beta, E alpha, and E beta mRNA expression but only minimal A alpha mRNA expression. In 11 primary B10.A B cell lymphomas with a normal I-A+, I-E+ phenotype, no imbalances in A alpha/A beta mRNA levels were observed. The implications of these findings for the role of class II MHC expression in mouse B cell lymphoma-genesis are discussed.

Divergent and invariant HLA class II beta chain isoelectric points

Class II molecules were isolated from consanguineous HTCs (DR1-DRw8) by sequential immunoprecipitation with the monoclonal antibodies 7.3.19.1 (anti-DRw52-like), B8.11.2 (anti-DR backbone), and 7.5.10.1 (anti-HLA class II backbone). Depending upon the DR-serotype of the cell line used, two or three class II antigen families, distinct in molecular weight, could be isolated (see Hum Immunol 9:221, 1984). Immunoprecipitated class II molecules were treated with NaNase and then analyzed on 1D-IEF gels. Each HLA class II antigen family contained two alpha chains conserved in pI. Furthermore, the various haplotypes show distinct electrophoretic beta chain patterns. The number of beta chain charge configurations detected varies from 2 to 5, depending upon the antigen family or haplotype studied. Some of these chains have a pI which is specific for a given class II serotype whereas other beta chain pIs are invariant and shared among more antigen families or haplotypes.

A study on class II antigens involved in the T cell proliferative responses to PPD using cross-reacting monoclonal antibodies in human and murine system

Two monoclonal antibodies (MoAb) 1E4 and ISCR3, which detect class II antigens across species barriers, were studied for their inhibitory effects on human and murine T cell proliferative responses to purified protein derivative of tuberculin (PPD). The 1E4 detected at least a polymorphic determinant on I-A molecules from mice carrying the H-2b haplotype, and the ISCR3 detected the Ia.7 determinant on I-E molecules. Nevertheless, both 1E4 and ISCR3 recognized monomorphic determinants on HLA-DR antigens (human I-E equivalent molecules), but not on HLA-DQ antigens (human I-A equivalent molecules). It was demonstrated that 1E4 significantly inhibited PPD-specific responses of T cells from Ib-bearing mice. In contrast, ISCR3 showed marginal effects on the responses of mice bearing Ia.7. However, in the human system both 1E4 and ISCR3 reduced proliferative responses to PPD. These results suggest that a functional difference exists between humans and mice in the I subregion products involved in the T cell proliferative responses to PPD.

Cells homozygous for two HLA-DR7-associated HLA-D specificities express highly similar DR molecules but different DQ molecules

The Ia molecules expressed by cells homozygous for two distinct HLA-DR7-associated HLA-D specificities, Dw7S and Dw11L, were compared. The complete Ia phenotypes of these cells are DR7, DRw53, DQw2, Dw7S, DPw4 and DR7, DRw53, DQw3, Dw11L, DPw4, respectively. Immunofluorescence analysis revealed that three DQ-specific monoclonal antibodies (Leu-10, 33.1, and HK-19), which detect polymorphic DQ determinants that do not correspond to known serologic specificities, are nonreactive with DR7, Dw7S cells but are reactive with DR7, Dw11L cells. The DR molecules isolated from Dw7S and Dw11L cells are very similar and comigrate when analyzed together by two-dimensional gel electrophoresis. In contrast, the DQ molecules isolated from these cells are structurally distinct: the DQ beta chains of DQw2-bearing molecules from Dw7S cells are very basic, while those of DQw3-bearing DQ molecules from Dw11L cells are more acidic. The finding that two DR7, D-different cells express indistinguishable DR molecules and structurally distinct DQ molecules documents a unique pattern of Ia molecular organization which is different from those previously described for the DR2-, DR4-, or DRw8-associated HLA-D specificities.

Gene products of the HLA-D region in normal and malignant tissues of nonlymphoid origin

Indirect immunofluorescence staining with monoclonal antibodies has shown a differential distribution of HLA-DR, DQ, and DP antigens in normal tissues of nonlymphoid origin. The distribution of HLA-DP antigens is similar to that of HLA-DR antigens, while that of HLA-DQ antigens is more restricted. Malignant transformation of cells of nonlymphoid origin may be associated with the appearance of the gene products of the HLA-D region. HLA-DR antigens appear more frequently than the other two types of HLA class II antigens and HLA-DP antigens more frequently than HLA-DQ antigens. Differential expression of the gene products of the HLA-D region was also found in autologous metastases removed from different anatomic sites from patients with melanoma. The HLA class II phenotype of surgically removed malignant lesions did not correlate with the degree of differentiation of tumor cells and/or with the expression and/or cellular distribution of HLA class I antigens. Furthermore, in melanoma lesions, no relationship was found between the HLA class II phenotype and the expression of 3 membrane bound and 1 cytoplasmic melanoma associated antigen recognized by monoclonal antibodies. The functional significance and the practical implications of the differential expression of the gene products of the HLA-D region by tumor cells are discussed.

Molecular characterization of three HLA class II molecules on DR4 and DRw9 haplotypes: serologic and structural relationships at the polypeptides level

By using alloantisera, three distinct HLA-D/DR region-encoded class II molecules were identified from cells carrying the HLA-DR4 and DRw9 haplotypes. Both DRw-53 and DQw3 molecules that bear the "supertypic" specificity were isolated independently from the DR antigen. The light chains of the DR4 antigens from different HLA-D types were distinct from one another, whereas the DRw53 molecules had identical charge and molecular weight in both heavy and light chains. On the other hand, the DQw3 molecules from the DR4 cell lines (Dw4 and Dw 10) were apparently identical but were polymorphic at least in the light chains among the DR4, DR5, and DRw9 haplotypes. In addition, monoclonal antibodies which specifically precipitate DR4 and DQw3 molecules have been isolated. The variable extent of homogeneity and diversity of three class II molecules may aid in our understanding of the role of class II antigens in the human immune regulation.

Differential susceptibility to modulation by recombinant immune interferon of HLA-DR and -DQ antigens synthesized by melanoma COLO 38 cells

Recombinant immune interferon (IFN-gamma) induced a dose-related increase in the synthesis and expression of HLA class II antigens by the cultured melanoma cells COLO 38. Although IFN-gamma-treated melanoma cells COLO 38 continue to express higher levels of HLA-DR antigens than of HLA-DQ antigens, the effect of IFN-gamma was more marked on HLA-DQ antigens than on HLA-DR antigens, as indicated by the dose and incubation time required to induce the changes and by the extent and duration of the increase. The effect of IFN-gamma on HLA class II antigens is significantly higher than that of leukocyte and fibroblast interferons. Analysis by one- and two-dimensional gel electrophoresis of antigens synthesized by melanoma cells COLO 38 in the presence of IFN-gamma did not detect any significant change in the structural profile of the subunits of HLA-DR and -DQ antigens.

A new allodeterminant on HLA-DQ molecules carrying the DQw3 specificity

The la subset that reacts with alloantiserum HON known to possess a strong anti-DRw53 activity was isolated from a 125I-labeled Ia preparation obtained from cells of RPMI 8057 cell line (DR1,4) and was found on peptide mapping to be lacking in the pattern characteristic of DR-like molecules carrying the DRw53 specificity and to display the structural features of DQ molecules, particularly those carrying the DQw3 specificity. Distribution analysis on a panel of selected la-positive cell lines indicated that the specificity involved is associated only with DR4 and DRw9, differing from the known DRw53 pattern (DR4, 7, and w9) and also from the known DQw3 pattern (DR4 and 5). Reciprocal sequential binding experiments demonstrated that the HON-defined specificity resides along with DQw3 specificity on the same molecules. Thus, HON alloantiserum possesses two different antibody activities; one directed to DRw53 specificity and another directed to a new DR4- and w9-associated DQ specificity.

Partial N-terminal sequence analysis of human class II molecules expressing the DQw3 determinant

HLA-DQ molecules were isolated from DRw9-homozygous and DR4-homozygous cell lines by using a monoclonal antibody HU-18, which recognizes class II molecules carrying the conventional DQw3 determinant. The partial N-terminal sequence analysis of the DQw3 molecules revealed that they have sequences homologous to those of murine I-A molecules. Within the limits of our sequence analysis, the DQw3 molecules from the two cell lines are identical to each other in both the alpha and beta chains. The DQ alpha as well as DQ beta chains were found to have amino acid substitutions when compared to other I-A-like molecules whose sequences have been reported. These differences may contribute to the DQw supertypic specificity. The polymorphic nature of DQ molecules is in marked contrast to that of DR molecules where DR alpha chains are highly conserved while DR beta chains have easily detectable amino acid substitutions.

Implication of structural class II gene polymorphism for the concept of serologic specificities

We have used DNA-DNA hybridization methods to study the relationship of genetic polymorphisms to the established HLA-D region determinants as detected with serological reagents. The supertypic determinants DRw52 and 53 are closely associated with a particular RFLP detected with the DR beta probe, but are seemingly encoded by a distinct beta gene compared to the "conventional" DR antigens. DQw1 is closely associated with a DQ alpha chain polymorphism, whereas the DQw2 and 3 specificities have correlations to RFLP using the DQ beta probe. Additional DQ polymorphism, in linkage disequilibrium with DR but yet without a serological counterpart is also described. Considering the finding that there exist a varying number of DR beta genes in different DR haplotypes (Böhme et al. 1985), from 1 in DRw8 to 3 (or 4) in DR4- and DR7-positive cells, we have made a tentative re-evaluation of the genetic basis for the conventional DR specificities. The combination of cell surface antigens encoded by DR and DQ loci are believed to form the basis for MLC stimulating determinants. We have speculated that a combination of determinants encoded by distinct DR beta genes and in certain instances additional DQ polymorphism is responsible for the DR types. Thus, only a limited variability is observed after DNA-DNA hybridization using DR beta probes. Only DR1-, 2- and 4-positive cells have distinct bands not detected in any other haplotypes, whereas DR3, 5, w6, and w8 can be characterized by a combination of bands, which is the result of hybridization with several DR beta genes. Furthermore, we have suggested that the difference between the DR3 and DRw6 specificities is due to variability with regard to 1 DQ beta gene, and have also made the assumption that DRw6 cells may express a lower concentration of DR locus encoded products compared to DR3-positive cells (Haziot et al. 1985). In addition, we have discussed the genetic basis for so-called DR blanks, implying that an unorthodox combination of DR and DQ determinants forms the basis for difficulties in assigning DR types to such cells in some cases and that "blanks" can be associated with low expression at the cell surface of well-known DR determinants. The use of cDNA and genomic probes for distinct class II genes to elucidate the mechanisms of HLA and disease association has been documented and discussed.

Genetic complexity and expression of human class II histocompatibility antigens

The genes encoding nearly all of the serologically defined class II antigens of the major histocompatibility complex have been isolated. Three class II loci have been studied in great detail. The DR region contains a single alpha gene and 3 beta chain genes, 1 of which is a pseudogene. The DR alpha chain gene has been linked to a DR beta gene which encodes a beta protein which contains the serological determinant MT3. A second cosmid cluster contains 2 beta genes, 1 of which encodes the DR4 allospecificity. The identification of these genes has been made by the comparison of amino terminal sequences of DR molecules obtained from a DR4 cell line and the deduced protein sequences of the beta 1 exons from cosmid and phage clones. A conserved element including the promoter and signal sequence is found at the 5' end of each of the 3 DR beta genes. Additionally, this element occurs three more times in the DR region, raising the question of whether additional beta chain genes might be found. The DQ region contains 2 pairs of genes, 1 of which encodes the DQ antigen. The 2nd pair of genes, called DX alpha and beta, appears to be capable of expressing a DQ-related product, although, to date, there is no evidence for its expression. The DP region also contains 2 pairs of genes. One pair encodes the DP antigen while the 2nd alpha-beta pair is shown to be composed of pseudogenes. The location of polymorphic regions in these genes and aspects of their relationship to the serology, evolution, and function of the class II MHC are discussed. The control of expression of class II genes by gamma-interferon has been examined. The promoters of class II genes are characterized by two conserved sequences common to all alpha and beta chain genes as well as by conserved sequences specific for either alpha or beta chain genes. In addition to studies of expression by DNA-mediated gene transformation, a system for the gene transfer of MHC antigens utilizing transmissible retrovirus vectors is described. Retrovirus vectors have been used to transmit DR alpha, DR beta, and the invariant chain (gamma) sequences to recipient cells with resultant expression of these proteins.

Nucleotide sequence of an HLA-DQ alpha chain derived from a DRw9 cell line: genetic and evolutionary implications

Three families of human Ia molecules, DP, DQ, and DR, have previously been defined. A cDNA clone, pDSH-9.1, encoding the alpha chain of a DQ molecule derived from an HLA-DRw9 homozygous cell line has been isolated and sequenced. Comparison of the nucleotide and predicted protein sequence to those of other DQ alpha subunits reveals that DQ alpha subunits derived from DR4, -7, and -9 cells are very similar to each other but quite different from a DQ alpha subunit derived from a DRw6 cell line. These studies suggest that certain Ia haplotypes have a common evolutionary history. Furthermore, in the context of current serologic and biochemical knowledge, they suggest that the gene encoding the DQ alpha subunit is in strong linkage disequilibrium with the DR locus.