Evidence for the separate molecular expression of four distinct polymorphic Ia epitopes on cells of DR4 homozygous individuals

An HLA-DRw53-restricted T-cell epitope from a novel Mycobacterium leprae protein antigen important to the human memory T-cell repertoire against M. leprae

Cellular immunity mediated by T cells plays a major role in protection against intracellular infections, including leprosy, a chronic disease caused by Mycobacterium leprae. In this work, we describe CD4+ T-cell clones, isolated from healthy humans immunized with M. leprae, which recognize a novel M. leprae protein antigen previously isolated from a lambda gt11 DNA expression library. On the basis of the deduced primary structure of the carboxyl-terminal part of the antigen, we have used a synthetic-peptide approach to exactly define the T-cell epitope recognized. Importantly, major histocompatibility complex restriction studies showed that the epitope is presented by an HLA-DRw53 molecule which is frequently expressed in many populations. In addition, we have demonstrated that a long-term cell-mediated immunity response against the peptide epitope is present after immunization with M. leprae. In conclusion, the M. leprae T-cell epitope described here fulfills the primary criteria for subunit vaccine candidates against leprosy.

Human T cells recognize mycobacterial heat shock proteins in the context of multiple HLA-DR molecules: studies with healthy subjects vaccinated with Mycobacterium bovis BCG and Mycobacterium leprae

Heat shock proteins (HSP) are considered to be important targets of the immune response to mycobacteria and, as such, relevant to subunit vaccine design. If HSP are major antigens in cell-mediated immunity, they should be recognized in the context of most of the HLA-DR molecules required for presentation of mycobacterial antigens to T cells. We tested peripheral blood mononuclear cells (PBMC) and T-cell lines from Mycobacterium leprae- and M. bovis BCG-vaccinated subjects for proliferation in response to the 18- and 65-kDa HSP of M. leprae, the 65-kDa HSP of M. bovis BCG, and the 70-kDa HSP of M. tuberculosis. Irrespective of HLA types, PBMC showing a strong response to M. leprae proliferated in response to mycobacterial HSP. HLA restriction analysis with T-cell lines showed that the M. leprae 18-kDa HSP was recognized in the context of HLA-DR4, HLA-Dw4, and HLA-DR1 molecules. The T-cell lines recognized the M. leprae 65-kDa HSP in the context of all of the HLA-DR molecules expressed by autologous antigen-presenting cells, i.e., HLA-DR1, HLA-DR2, HLA-DR5, HLA-DR7, and importantly HLA-DR4 (HLA-Dw4 and HLA-Dw14), which is relevant to autoimmunity. The M. tuberculosis 70-kDa antigen was also presented to the T-cell lines by HLA-DR1, HLA-DR2, HLA-DR5, and HLA-DR7 molecules. In addition, this HSP was recognized in the context of the HLA-DRw53 molecule, which is frequently expressed in many regions where leprosy is endemic. The T-cell lines proliferating in response to a given HSP lysed autologous monocytes-macrophages pulsed with that HSP. The results demonstrate that PBMC from individuals immunized with M. leprae respond to mycobacterial HSP and that these HSP are presented to T cells by multiple HLA-DR molecules, a prerequisite for their application in the next generation of subunit vaccines.

Autoreactive T cells from a type I diabetic recognize multiple class II products

Mononuclear cells obtained from a child at the acute presentation of type I diabetes were stimulated in vitro with human insulin followed by IL-2 and IL-4. All of the T-cell clones isolated from this stimulation were autoreactive, recognizing autologous B cells in the absence of insulin or other exogenous antigens. Eleven CD4+ clones were studied in detail to identify the class II MHC antigens stimulating these autoreactive cells. The donor was heterozygous for DR3DQw2 and DR4DQw3.2 haplotypes, a combination of alleles with a greatly increased risk for type I diabetes. The clones demonstrated skewed recognition of class II antigens. Three clones appeared to recognize a peptide derived from one class II beta chain (DR beta 1, DR4Dw4) presented by another class II beta chain (DR beta 4, DRw53). Three clones were stimulated by cells expressing DPw4 molecules. Only one clone recognized a product derived from the DR3 haplotype. In contrast to both antigen-specific and autoreactive T-cell clones derived from normal individuals, many of the autoreactive T cells isolated from this subject were stimulated by class II molecules other than DR beta 1. The results support the hypothesis that autoreactive T cells recognize autologous peptides in association with MHC and some of these peptides are derived from self MHC molecules.

Critical role of HLA-DR beta 1 residue 58 in multiple polymorphic epitopes recognized by xenogeneic and allogeneic antibodies

In a previous study, we identified glutamic acid at position 58 in DR (beta 1*1101) as critical for the epitopes recognized by the DRw11-specific mAb GS88.2, as well as the I-LR1 mAb that recognizes a polymorphic epitope on DR(alpha,beta 1*1101) and some DP molecules. The purpose of this study was to determine whether other polymorphic residues contribute to these epitopes and whether DR beta glutamic acid or alanine 58 and DP beta glutamic acid 56, the analogous position in DP beta, contribute to epitopes recognized by other anti-class-II mAb and allosera. Site-directed mutagenesis and transfection were used to produce cells bearing wild-type or mutant class II molecules that were analyzed with mAbs by flow cytometry and with human allosera by absorption and subsequent microcytotoxicity assays. These studies demonstrate that the residue at DR beta position 58 plays a central role in at least three different mAb epitopes and an epitope recognized by anti-DRw11 allosera. Substitution of glutamic acid for alanine at position 58 of eight DR beta chains caused gain of binding of four mAbs to all of the mutant molecules, except DR(alpha,beta 4*0101). These data suggest that the side chains of DR beta 58 and DP beta 56 point outward from the alpha-helix and directly contact antibody.

Class II major histocompatibility complex gene sequences in rheumatoid arthritis. The third diversity regions of both DR beta 1 genes in two DR1, DRw10-positive individuals specify the same inferred amino acid sequence as the DR beta 1 and DR beta 2 genes of a DR4 (Dw14) haplotype

The DR1 and DRw10 beta 1 chain genes were isolated from each of 2 individuals with rheumatoid arthritis who were heterozygous for these class II major histocompatibility complex specificities. The sequences of the DR1 beta 1 chains from both patients were identical, differing from previously reported DR beta 1 chains of individuals without RA by 2 amino acid substitutions, at positions 85 (Val-Ala) and 86 (Gly-Val), and by a silent mutation at the last nucleotide of codon 78 (C-T), resulting in the loss of a Pst I restriction endonuclease site. Identical DRw10 beta 1 chain genes were found in both patients. These were shown to encode the epitope recognized by monoclonal antibody 109d6. This antibody also recognizes an epitope on the DRw53 beta 2 chain of the DR4 haplotype. The third diversity regions of the DR1 beta (amino acids 67-74) and the DRw10 beta 1 chains (amino acids 67-73) were identical, respectively, with those of the DR4 (Dw14) beta 1 and beta 2 chains, raising the possibility that in these patients, the third diversity regions of the two DR beta 1 chain genes present in trans are conformationally equivalent to the cis-encoded third diversity regions of the DR4 (Dw14), DR beta 1, and beta 2 chains. The nucleotide sequences of the DQ beta complementary DNA clones were identical to that of the DQw1 beta chain, and no DR beta 2 complementary DNA clones were identified.

HLA-Dw14 and HLA-DR3 haplotypes share a functional determinant recognized by a human alloreactive T-cell clone

In the process of studying the fine specificity of HLA class II molecules, we identified an alloreactive T-cell clone raised to a HLA-Dw14 homozygous cell line that was specifically stimulated by Dw14+ homozygous typing cells but negatively with cells expressing the HLA-Dw4,-Dw10, -Dw13, and -Dw15 subspecificities of DR4. Of interest, this clone was also equivalently activated by stimulation with all DR3 cells and cell lines tested. Negative responses were obtained using a panel of 87 non-DR3 and non-Dw14 cells, including cell lines of the Tenth Histocompatibility Workshop. A monoclonal antibody inhibition study revealed the relevant stimulating determinant to be on HLA-DR molecules in both Dw14- and DR3-positive cells. A comparison of the DR beta 1-chain-inferred amino acid sequences suggests that formation of a topologically equivalent stimulating determinant would involve the participation of two noncontiguous regions of the third diversity region of DR beta 1. The putative recognition conformation detected by the clone is most probably specified by the presence of a valine at position 86 and a nonnegatively charged residue at positions 70, 71, and 74, since these are the only residues where DR3 and Dw14 are distinguishable from all other HLA-DR types. These findings illustrate that the functional ability of class II molecules is not necessarily either illustrated or predicted by serologic typing or by simple considerations of amino acid sequence.

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.

Differential expression of Ia antigens by rheumatoid synovial lining cells

The differential expression of Ia antigens was studied in freshly isolated rheumatoid nonlymphoid synovial lining cells (SLC) and rheumatoid synovial fibroblast cell lines cultured in the presence of Interferon-gamma, using a large panel of anti-Ia reagents with monomorphic or polymorphic specificities. All the HLA-DR or -DQ specificities detectable on the corresponding peripheral blood B cells were also expressed in freshly isolated SLC. However, in all instances, the number of DR-positive SLC exceeded the percentage of cells expressing DQ antigens. In addition, the epitope expression of Ia antigens varied within the DR or DQ populations of Ia molecules as revealed by polymorphic reagents. Double-label experiments or using the ingestion of Latex particles as a marker demonstrated that the synovial macrophages (type I SLC) primarily bear the DR+DQ+ phenotype, while there is an additional population of nonphagocytic SLC (previously termed type II SLC) that has a DR+ and monocyte marker negative phenotype but did not have detectable levels of DQ antigens as analyzed by both fluorescence microscopy and cell sorter analysis. This latter population frequently had a morphology showing dendritic processes and rapidly lost the expression of Ia antigens upon culture. Cells with a similar, primarily DR+ phenotype were readily obtained in synovial fibroblast cultures after treatment with Interferon-gamma. These data suggest that there are two populations of Ia+ synovial lining cells: the synovial macrophages (type I cells) with the DR+DQ+ phenotype, and cells probably related to fibroblasts with a DR+ phenotype without detectable DQ antigens (type II cells). The fact that the latter phenotype could be induced by Interferon-gamma treatment of cultured synovial fibroblasts suggests that this mediator may have a similar role in vivo in the activation of certain synovial cell populations.

Determination of the HLA-DR profile of an HLA class II negative carcinoma cell line by restriction fragment length polymorphism (RFLP) analysis

The human colonic adenocarcinoma cell line HT-29 does not normally express HLA class II molecules. By restriction fragment length polymorphism (RFLP) analysis of DNA with a DR beta-probe, we analysed the genomic DR beta polymorphism of this cell-line, and compared it with the RFLP patterns seen in DNA from a reference panel of different DR homozygous and heterozygous cells. The HT-29 cell-line expressed DR beta fragments similar to the sum of the fragments expressed by DR4 and DR7 homozygous cells. The DR4 and DR7 haplotypes of HT-29 was further confirmed by comparing the RFLP patterns of four DR4/7 heterozygotes with that of HT-29. Furthermore, the HT-29 cell line expressed a Hind III 9.3 kb fragment previously found to be strongly associated to DRw53. Following treatment with gamma-interferon, the HT-29 cells could be induced to express class II molecules. Serological typing revealed the presence of the DR4, DR7 and DRw53 antigenic determinants.

Induction of various HLA class II molecules in a human colonic adenocarcinoma cell line

The colonic carcinoma cell line HT-29 had no constitutive expression of HLA class II molecules. Gamma interferon (IFN-gamma) induced expression of HLA class II molecules in a dose-dependent manner with 100 U/ml as an optimal dose. The expression of HLA-DR, HLA-DP, and HLA-DQ molecules seemed to follow different kinetics. While DR and DP molecules were maximally induced after 2 days, DQ molecules appeared later with maximum percentage positive cells after 8 days. Treatment with a prostaglandin synthesis inhibitor (indomethacin) neither induced class II expression nor altered the dose-response curve for IFN-gamma; this indicated that possible endogenous production of prostaglandins in this cell line did not interfere with its class II expression. The lectins phytohaemagglutinin (PHA), concanavalin A (Con A), pokeweed mitogen (PWM), and wheat germ agglutinin (WGA) did not induce class II expression.

Changes in cell surface antigen expression on human articular chondrocytes induced by gamma-interferon. Induction of Ia antigens

Ia antigens (class II HLA molecules) have been detected on cells eluted from affected human cartilage in certain disease states, but not on normal cartilage cells. Because the presence of Ia antigens on chondrocytes may play an important role in rheumatic diseases, we investigated the induction of these molecules by gamma-interferon (gamma-IFN), a potent Ia-inducing lymphokine. Human articular chondrocytes were incubated with recombinant gamma-IFN, and the expression of Ia antigens was studied by cell sorter analysis, using a panel of reagents that detect monomorphic and polymorphic specificities of the DR and DQ Ia antigen families. While the induction of DR antigens, including polymorphic DR specificities, was readily obtained with gamma-IFN (50-95% positive cells), DQ antigens were negative or were displayed only on a lower percentage of chondrocytes (5-60%). In addition, incubation with gamma-IFN led to an increased expression of HLA class I antigens. The expression of various other surface markers either remained unchanged (as in 4F2 and BA-2) or showed tendencies toward decreased percentages (as in 83c2) or increased percentages (as in M phi R-17). No apparent change in cell morphology or growth pattern was observed.

HLA-DR beta gene DNA polymorphisms revealed by Taq I correlate with HLA-DR specificities

Human genomic DNA digested with restriction endonuclease Taq I was hybridized with cDNA probes for DR beta and DQ beta, for correlation of restriction fragment length polymorphisms with HLA-DR specificities. DR beta Taq I RFLPs were distinctive for DR serological types 1 to w9, with the exception of DR3 and w6, and were markedly consistent within DR specificity. Some common variants in RFLPs did emerge within serological type; DR3, e.g., was associated with two different fragment patterns, one of which occurred on the A1.B8.DR3 haplotype and was linked with a DR alpha Bgl II variant, and the other on the B18.DR3 haplotype. In the Pacific specimens examined, RFLPs were, with few exceptions, similar to those seen in Caucasoids sharing the same DR specificity. This study indicates that genomic hybridization is a useful adjunct to serological and cellular class II typing and should be particularly informative in identifying new HLA-DR alleles in populations serologically less well-defined than Caucasoids.

Definition of a possible genetic basis for susceptibility to acute myelogenous leukemia associated with the presence of a polymorphic Ia epitope

The polymorphic Ia epitope recognized by monoclonal antibody 109d6 is detectable on the leukemic cells of a significantly increased number of individuals with acute myelogenous leukemia, compared with its frequency in normal healthy control individuals. In control individuals, the presence of the 109d6 epitope is closely correlated with but not identical to the DRw53 allo-specificity. However, the frequency of particular conventional Ia allodeterminants, including DRw53, is not significantly elevated in the leukemia group. Considerable evidence supports the conclusion that the high frequency of the 109d6 epitope reflects an inherited basis for susceptibility to the development of acute myelogenous leukemia and not a differentiation event occurring in the leukemic lineage. The 109d6 determinant is expressed by leukemic myeloblasts as well as by homologous normal B cells and monocytes obtained from the same individuals during remission of the leukemia. Furthermore, in healthy family members the 109d6 epitope is encoded by Ia haplotypes that are shared with the patient. Of special interest, certain of these haplotypes have combinations of the 109d6 epitope and Ia specificities not commonly seen in normal individuals; here, also, healthy family members share these haplotypes.

Structural organization of the DR subregion of the human major histocompatibility complex

Two clusters of overlapping cosmid and lambda phage clones comprising 205 kilobases (kb) have been isolated from the DR subregion of the human major histocompatibility complex from a DR4 haplotype. A single DR alpha and three DR beta genes were identified. In one cluster (135 kb), the DR alpha gene is 90 kb distant from the DR beta gene encoding a molecule that carries the MT3 serological specificity. In the second cluster (70 kb), the DR beta gene determining the DR4 specificity is located 22 kb apart from a DR beta pseudogene (DR beta psi). A 3- to 4-kb sequence located at the 5' end of the DR beta (MT3) gene is common to all three DR beta-chain genes. In addition, three more copies of this sequence are spaced between the DR alpha and the DR beta (MT3) genes in the first cluster and one of these, at least, is associated with a DR beta 1 exon, suggesting that additional genes could be encoded in this region and that multiple duplication events have led to its evolution.

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.

Interdependent membrane mobility of human MHC coded antigens detected by monoclonal antibodies to various epitopes on class I and II molecules

Binding of monoclonal antibodies (MAB) to human MHC coded class I antigens, w6.32HL or 61D2, specifically leads to clustering of these antigens and their assembly at one polar site on a cell, whereby these class I antigens tow class II-antigens with them into the polar cap revealing preexisting or arising molecular complexes in the membrane of the living cell. These class II antigens included DR (seen by MAB 2MC3, L203, L227, I-LR2, 109d6, SFR-3) and DQ (seen by Genox 3.53 and IVD12). In analogous cocapping experiments employing MAB to various class II antigens, interdependent surface mobility (bidirectional cocapping) could be demonstrated between DRw52 (MT2, seen by I-LR2) and DQw3 (MB3, seen by IVD12) as well as between DRw53 (MT3, seen by 109d6) and DQw3. There was incomplete interdependence between DRw52 or DRw53, respectively, and other DR antigens (seen by L227). These latter antigens were independent from DQ (seen by Genox 3.53 or IVD12). Analyzing pairs of monoclonal antibodies with various specificities to determinants on class I or II molecules a frequent finding was unidirectional cocapping: here a first antibody cocapped epitopes seen by a second, but this antibody did not cocap epitopes seen by the first. We conclude that epitopes are irregularly distributed on MHC coded molecules or on complexes of these molecules.

Identification, at the genomic level, of an HLA-DR restriction element for cloned antigen-specific T4 cells

Two T4 cell clones (TLC) specific for antigenic epitopes on Chlamydia trachomatis were studied. Using a panel of allogeneic antigen-presenting cells (APC), both TLC were found to be restricted by HLA class II elements closely associated with, but not identical to the DRw5S specificity, as determined by highly selected alloantisera, a monoclonal antibody (mAb), 109d6, and confirmed on the DNA level by determination of restriction fragment length polymorphisms (RFLP) with a DR beta probe. Furthermore, HLA-DR-specific mAb, including 109d6, but not other HLA class II- or class I-specific antibodies inhibited the two TLC, strongly suggesting that the restriction element is expressed by a DR molecule. Using digestion with Hind III restriction enzyme and a DR beta probe, we found a complete concordance between the appearance of a 9.3 kilobase band and the ability of allogeneic APC to restimulate the T cell clones. Thus, the restriction element for these T cell clones appear to be expressed by DR molecules, but can, at present, only be detected at the genomic level.

Molecular localization of human class II MT2 and MT3 determinants

The specificities of the monoclonal antibodies I-LR2 and 109d6, which recognize MT2- and MT3-like serologic determinants, respectively, have been confirmed by panel testing. In addition, the relationships of these antibodies to other monoclonal antibodies and alloantisera have been studied by means of cell surface fluorescence, complement-dependent cytotoxicity and immunoprecipitation. Using these monoclonal antibodies, molecules encoded by the HLA-D region have been isolated and characterized by amino acid sequencing and peptide mapping. By these criteria, the major populations of molecules bearing MT2- and MT3-like determinants are indistinguishable from DR molecules.

Strong association of rheumatoid arthritis with the presence of a polymorphic Ia epitope defined by a monoclonal antibody: comparison with the allodeterminant DR4

Among individuals with rheumatoid arthritis the presence of the polymorphic Ia antigen epitope detected by the monoclonal antibody 109d6 is more strongly correlated with disease susceptibility than are other specificities, such as HLA DR4, DRw53 (MT3) or the antigenic determinant, defined by the monoclonal antibody 17-3-3S. The cells of 93% of Caucasian and Hispanic patients react with the 109d6 reagent. As was the case in normal individuals, all DR4-positive patients express the 109d6 determinant; however, 26% of those with rheumatoid arthritis have the epitope recognized by antibody 109d6, but lack the specificity DR4. Of these, one-third expresses only HLA DR1 and DQw1 (MT1, MB1) determinants. Studies of family members reveal that here the determinants 109d6, DR1, and DQw1 are encoded by the same unusual haplotype. In certain other individuals with rheumatoid arthritis who express DR4, DRw53, and the 109d6 determinants, family studies show that the 109d6 epitope is encoded not only by the haplotype specifying DR4 but also by the opposite haplotype that does not bear the genes for DR4. This suggests that homozygosity for certain Ia epitopes is relevant to determining the disease-susceptibility state. These studies emphasize the utility of monoclonal antibodies as reagents for the recognition of Ia epitopes that are more closely involved in the determination of disease susceptibility than are allomorphic molecules detected by conventional typing alloantisera.