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

The major histocompatibility complex gene region and sarcoidosis susceptibility in African Americans

Investigators have intensively evaluated the major histocompatibility (MHC) complex for sarcoidosis susceptibility genes with the majority of reports implicating the human leukocyte antigen (HLA)-DRB1 gene. Because most studies have been performed in white and Asian populations, we sought to determine which MHC genes might be risk factors for sarcoidosis in African Americans. We genotyped six microsatellite markers spanning 11.6 megabases that overlapped the MHC region on chromosome 6p21-22 in 225 nuclear families ascertained by African American probands with a history of sarcoidosis. Using a family-based association methods approach, we performed multiallelic tests of association between each marker and sarcoidosis. A statistically significant association was detected between sarcoidosis and the DQCAR marker (p = 0.002) less than two kilobases telomeric from the HLA-DQB1 gene. Typing two additional markers in this region revealed that DQCAR-G51152 haplotypes, spanning a 38-kilobase region across the HLA-DQB1 gene, were associated with sarcoidosis on a global level (p = 0.022). Analysis of individual DQCAR and G51152 alleles showed that the DQCAR 178 (expected = 21.0; observed = 10; p = 0.0005) and G51152 217 (expected = 25.6; observed = 14; p = 0.0009) alleles were transmitted to affected offspring less often than expected; whereas the DQCAR 182 allele was transmitted more often than expected (expected = 52.6; observed = 66; p = 0.002). Our results indicate that HLA-DQB1 and not HLA-DRB1 plays an important role in sarcoidosis susceptibility in African Americans. Identification of the specific HLA-DQB1 alleles that influence sarcoidosis susceptibility in African Americans and the study of their antigenic-binding properties may reveal why African Americans suffer disproportionately from this disease.

Interactions between staphylococcal superantigens and human T-cell clones are predominantly but not exclusively governed by their T-cell receptor V beta usage

Staphylococcal exotoxins (SE) are potent mitogens for human and murine T cells. Extensive studies in mice have demonstrated strict correlations between T-cell responses to individual SE and TCR V beta expression. Studies examining the TCR V beta expression of SE-activated human peripheral blood T cells also suggest close correlations, whereas the data reported using human T-cell clones (TCC) are conflicting. We have determined the cDNA TCRB sequences of 52 different human TCC, expressing 35 different T-cell receptor V beta (TCRBV)-encoded sequences. The TCC were tested in proliferative assays using nine different SE. Most of these TCC express V beta s which have not been tested previously in studies examining interaction between TCC and SE. The SE stimulated a variable fraction (1/48-31/52) of the TCC. The ability of a given SE to stimulate TCC in many cases correlated with V beta expression, but several exceptions were found. With one possible exception, comparisons between deduced amino-acid sequences within the 'fourth hypervariable region' of the TCR beta chain and SE responsiveness did not reveal potential SE binding motifs. We conclude that the reactivity of T cells towards SE is governed mainly by their TCR V beta expression. However, the authors' results also suggest that the interaction between SE and human T cells may involve elements unidentified as yet which are in addition to the beta chain of the TCR.

Characterization of an HLA-DR15 DQ5 haplotype found in the Spanish caucasoid population

HLA class II typing by RFLP and PCR-SSOP has been performed on HLA-DR2-positive individuals as a part of a study on MHC in a Spanish Caucasoid population. The results of this study reveal that HLA-DR15 (DRB1*1501 DRB5*0101) and DQ5 (DQA1*0102 DQB1*0501/0502) are not uncommonly associated in such a population. Family segregation has been assessed and allogeneic reactivity against some classic DR2 haplotypes has been tested; a stimulatory capability of DQ6 antigen in this situation is shown. It is suggested that the reported association is not uncommon in European Caucasoids as well as in other populations and it should be considered in matching for transplantation and in DR2-associated diseases.

T-cell responses against products of oncogenes: generation and characterization of human T-cell clones specific for p21 ras-derived synthetic peptides

Peptides derived from mutated human proto-oncogenes bound to HLA may represent a novel type of tumor-specific antigen. Mutated ras genes are the oncogenes most frequently identified in human cancer. The transforming genes carry a mutation in codons 12, 13, or 61. We have investigated whether the T-cell repertoire of healthy individuals contains T cells capable of recognizing and responding to oncogene-derived peptides. Synthetic peptides derived from mutated p21 ras proto-oncogenes, covering mutations at codons 12 or 13 were selected. It was feasible to elicit T-cell responses and isolate several new T-cell clones (TCC) with specificity for a number of different mutated ras peptides after repeated in vitro immunization. Four TCC were characterized with respect to fine specificity and HLA restriction. TCC B and I were restricted by HLA-DR molecules, and recognized the mutated p21 ras-derived peptide carrying Arg and Lys at residue 12, respectively. TCC E and F were restricted by HLA-DQ molecules, the former being specific for a mutated p21 ras-derived peptide with Val in position 13 and the latter more broadly reactive. Peptide competition experiments with a panel of ten peptides derived from p21 ras indicated that all could bind to HLA-DQ molecules of the T-cell donor, while several were also able to bind his HLA-DR molecules. These results show that several p21 ras mutations resulting in aa substitutions at residues 12 or 13 could be recognized by T cells derived from precursor T cells of relatively low frequency present in the normal repertoire of a single donor.

Insulin dependent diabetes mellitus susceptibility or protection may be determined by certain HLA-DQ molecules

On the basis of our own studies and those of others, we suggest that several DQ molecules may be involved in IDDM susceptibility (Table 2). Our studies suggest that these DQ molecules may be encoded both when the DQA1 and DQB1 genes are in cis or trans position. A common denominator of several of these IDDM susceptibility molecules is that they have a non-Asp amino acid at DQ beta chain residue 57. Our studies demonstrate that this residue may be an important residue for peptide presentation to T cells.

Critical role for the Val/Gly86 HLA-DR beta dimorphism in autoantigen presentation to human T cells

Helper T lymphocytes recognize fragments of foreign (or self) antigens in the peptide-binding clefts of major histocompatibility complex class II molecules; their activation is a crucial step in the induction of many immune and autoimmune responses. While studying the latter, we raised a T-cell line from the thymus of a myasthenia gravis patient against recombinant alpha subunit of the human acetylcholine receptor, the target of this autoimmune disease. The line responds to the 144-156 region of the human sequence and not to the same region of the electric fish homolog, which differs by only three residues. These CD4+ T cells recognize this epitope only in the context of HLA-DR4 class II molecules, of which the variants with Gly86 are absolutely required. Thus the naturally occurring alternatives Dw14.2 (Gly86) and Dw14.1 (Val86)--which differ only at this one position in the entire antigen-binding region--show an all-or-nothing difference in presenting activity. This dimorphism at position 86 is widespread, occurring in subtypes of DR1, DR2, DR3, DR5, and DR6 alleles as well as DR4. Since other DR4 subtypes with substitutions at positions 70-74 also fail to present this peptide, and glycine residues can be uniquely flexible, we suggest that this replacement at position 86 acts locally or at a distance by altering the conformation of the peptide-binding cleft. Such profound functional consequences for T-cell recognition as we report here may explain this example of conserved major histocompatibility complex diversity.

T cell defined HLA epitopes and T cell receptor polymorphism in insulin dependent diabetes mellitus

T cell defined epitopes on class II HLA molecules (epitopes distinguishable by T cells but not by antibodies) seem to be important determinants of IDDM susceptibility/resistance. Although HLA-DR4 is associated with IDDM in many populations, DR4-positive HLA haplotypes vary greatly (relative risk from greater than 10 to less than 1). This variation seems to depend on both the DQ allele and T cell defined subtypes of the DR4 allele. These IDDM associated alleles at the two loci (DQB1 and DRB1) are not correlated with each other in the healthy population, so they clearly are independent risk factors. HLA-DR2 has universally been associated with lack of IDDM, and seems to be protective. However, not all DR2 haplotypes protect, and the protection or lack of protection correlates with T cell defined subtypes of DR2. In this case, however, the DR2 subtypes do correlate with DQ alleles, so it is unclear which locus (loci) is (are) actually affecting the disease process. It may be significant that, for both DR2 and DR4, only the more protective subtypes have arginine at amino acid position 71. Other portions of the DR beta chain are clearly important, however. Although TCR alpha and beta seemed to be promising candidates for additional IDDM susceptibility genes, in fact the various TCR alpha and beta haplotypes are equal, or nearly equal, with regard to IDDM susceptibility. The importance of HLA alleles in IDDM susceptibility, and the lack of importance of TCR alpha and beta alleles, may be due to the different means by which the HLA and TCR molecules achieve antigen binding diversity: HLA molecules by multiple loci and allelic diversity, and TCR molecules by the tremendous diversity that can be generated from a single TCR allele during T cell maturation.

Alloreactive T-cell clones identify multiple HLA-DQw3 variants

HLA-DQw3 is a broadly defined alloantigen that has been subdivided by serological, biochemical, and molecular methods into three distinct specificities: DQw7, DQw8, and DQw9. In order to characterize functionally relevant structural polymorphisms within this family of alloantigens, we generated a series of DQw3-reactive T-cell clones that together recognize six different variants of DQw3. T-cell clones IG11 and IG9 were found to recognize three distinct functional variants associated with a majority of DQw3+ cells, while clones 21J, IE6, 64B, and IC3 recognized four more narrowly distributed functional variants associated with unique DQw7, DQw8, and DQw9 subsets. Comparison of known DQB gene sequences suggested candidate recognition sites for clones IG11 and 64B in the region of amino acid residues 66 to 71 and residue 57 of the DQ beta chain. In contrast, no unique DQB or DQA sequences were found that individually corresponded to the reactivity patterns of clones 21J, IE6, IG9, or IC3, suggesting that an interaction between DQ alpha and DQ beta chains determines allo-recognition. These data are consistent with the hypothesis that T cells recognize specific alloepitopes on HLA class II molecules, either as distinct structural elements that trigger an alloresponse or, more indirectly, as contact elements that influence alloreactivity by governing the binding of foreign peptide. The results illustrate the diversity of possible T cell responses directed toward HLA-DQ molecules and suggest that T cell recognition of the DQ heterodimer alone, or a peptide antigen bound to the DQ heterodimer, can be affected either by the individual DQ alpha and beta chains, or by a more complex interaction between the two.

Antigen-specific T cells restricted by HLA-DQw8: importance of residue 57 of the DQ beta chain

CD4+ T-lymphocyte clones reactive with antigen from herpes simplex virus type 1 were established from a DQw8+ donor. One T-lymphocyte clone was able to recognize HSV antigen only when presented by antigen presenting cells expressing DQw8, and only HLA-DQ-specific mAbs could inhibit the response. Using antigen presenting cells from an extensive panel of donors whose HLA-DQ molecules and genes had been established, it could be demonstrated that alanine at residue 57 of the DQ beta chain played a critical role in presentation of herpes simplex virus--derived antigen(s) to T cells. The results are interesting, since the amino acids present at residue 57 of the DQ beta chains seems to play an important role in determining susceptibility to develop or protection against insulin-dependent diabetes mellitus.

T-cell recognition of HLA class II molecules induced by gamma-interferon on a colonic adenocarcinoma cell line (HT29)

HLA class II molecules may be induced on non-lymphoid cells by gamma-interferon (IFN-gamma). We investigated if HLA class II molecules induced by IFN-gamma on the HT29 colonic carcinoma cell line are functional, i.e. if they may be recognized by allogeneic T cells. We found that IFN-gamma-treated HT29 (HT29IFN) cells could not induce primary proliferative responses of peripheral blood T lymphocytes, nor were they able to induce proliferation in T-lymphocyte clones (TLC) specific for HLA class II molecules found on HT29IFN. However, in the presence of exogenous interleukin 2 (IL-2), 1 of 5 DQw8-specific TLC proliferated when restimulated with HT29IFN, and 3 of these 5 TLC could very effectively inhibit the growth of HT29IFN, probably due to a cytotoxic effect. Both the proliferative response and the cytotoxicity were inhibited by anti-DQ MoAb. We conclude that T cells may recognize HLA-DQ molecules on non-lymphoid cells, which may be of relevance for autoimmune diseases, graft-versus-host disease, and possibly for the recognition of malignant cells.

Genetic control of autoimmunity in type 1 diabetes

DNA sequence analysis of major histocompatibility complex (MHC) class II genes from humans and rodents with type 1 (insulin-dependent) diabetes indicates that a portion of MHC-linked genetic susceptibility in humans is determined by the HLA-DQA1 and -DQB1 loci. In this article John Todd summarizes recent advances in these studies. The conformation of DQ molecules and their levels of expression may influence the efficiency of autoantigen presentation and the degree of pancreatic beta cells destruction during disease development. Certain DAQ1 and DQB1 alleles correlate with decreased susceptibility to disease. The penetrance of class II alleles that are correlated with positive susceptibility may be influenced by environmental factors such as bacterial and viral infections.

The A3 allele of the HLA-DQA1 locus is associated with susceptibility to type 1 diabetes in Japanese

Analysis of the frequencies of class II HLA-DR and HLA-DQ alleles by serological and DNA typing in 49 Japanese patients with type 1 (insulin-dependent) diabetes and 31 Japanese controls indicates the following. (i) Susceptibility is more strongly associated with the HLA-DQ subregion than with the HLA-DR subregion. (ii) Of the class II alleles detected, the A3 allele of the DQA1 locus was the most strongly associated with disease. Ninety-six percent of the patients were positive for the A3 allele compared to 53% of the controls (P = 0.001; relative risk = 19.7; confidence limits = 3.72-188.64). (iii) The DQw8 allele of the DQB1 locus, which is associated with susceptibility to type 1 diabetes in Caucasians and Blacks, was not increased in frequency in Japanese patients (22%) versus controls (19%). (iv) Asp-57-encoding DQB1 alleles are associated with reduced susceptibility to type 1 diabetes in Caucasians. The major predisposing haplotypes in Japanese are DR4 and DR9. By DNA sequence analysis, both of these Japanese haplotypes have Asp-57-encoding DQB1 alleles. Oligonucleotide dot blot analysis showed that all, except 1, of the 49 Japanese patients and all of the 31 controls have at least one Asp-57-encoding DQB1 allele. In addition, 40% of the patients were homozygous for Asp-57-encoding DQB1 alleles versus 35% of the controls. The high frequencies of Asp-57-encoding DQB1 alleles in this ethnic group may account for the rarity of type 1 diabetes in Japan.

HLA-DQ antigens and DQ beta amino acid 57 of Japanese patients with insulin-dependent diabetes mellitus: detection of a DRw8DQw8 haplotype

DQw8 (DQw3.2) on DR4 haplotypes is a susceptibility gene for development of insulin-dependent diabetes mellitus (IDDM) in Caucasoids, possibly because it encodes a non-Asp amino acid (aa) (i.e. Ala) at residue 57 of the DQ beta chain (non-Asp-57). Most Caucasoid IDDM patients are homozygous non-Asp-57. We have examined 14 Japanese IDDM patients, selected to be either DR4 or DRw9 (associated to IDDM among Japanese). Their DQB1 alleles and the aa encoded by their DQB1 codons 57 were identified, using 11 different sequence-specific oligonucleotide probes. Secondly, they were examined with DQw8 specific T lymphocyte clones and with anti-DQ monoclonal antibodies. The DQB1 genes on their DR4 and DRw9 haplotypes in all cases encoded Asp-57. Two patients were Asp-57 homozygous, the rest were Asp-57/non-Asp-57 heterozygous. The DR4 haplotypes all carried DQw4 (rather than DQw8), and the DRw9 haplotypes all carried DQw9. Furthermore, five of six DRw8 positive patients carried a previously undetected DRw8DQw8 haplotype, where both the DQA1 and DQB1 genes were similar to those usually found on the DR4DQw8 haplotype. Thus, the DR/DQ allele combinations and aa residue 57 of the DQ beta chain of Caucasoid and Japanese IDDM patients are largely different.

Human T lymphocyte clones: influence of culture conditions and optimization of proliferative assays

Many CD4+ human T lymphocyte clones (TLC) are found not to proliferate against appropriate stimulating cells, and many lose this capacity during culture. This may be due, not to a defect in the recognition of the antigen, but to an inability to produce sufficient amounts of interleukin 2 (IL-2) for autocrine growth, since specific HLA-restricted proliferative responses could be induced in 'non-proliferative' clones by the addition of exogenous IL-2 or phorbol myristate acetate (PMA). Of various factors tested during expansion procedures of the clones, the proliferative capacity could only be restored by changing the stimulatory cells from B lymphoblastoid cell lines (B-LCL) to peripheral blood mononuclear cells (PBM). The cytotoxicity of the TLC was found to be independent of its proliferative capacity. After restoration of the proliferative capacity, a mouse B lymphoma cell line transfected with the appropriate HLA DQA and DQB genes was still not able to induce proliferation in the absence of exogenous IL-2. We conclude that (1) 'non-proliferative' TLC may recognize their targets, but fail to proliferate due to temporary lack of IL-2 production, and (2) even 'proliferative' T cells may fail to respond to certain target cells carrying the specific antigen, such as a murine transfectant, in the absence of exogenous IL-2.

Identification of susceptibility loci for insulin-dependent diabetes mellitus by trans-racial gene mapping

INSULIN-dependent (type I) diabetes mellitus (IDDM) follows an autoimmune destruction of the insulin-producing beta-cells of the pancreas. Family and population studies indicate that predisposition is probably polygenic. At least one susceptibility gene lies within the major histocompatibility complex and is closely linked to the genes encoding the class II antigens, HLA-DR and HLA-DQ (refs 3, 4). Fine mapping of susceptibility genes by linkage analysis in families is not feasible because of infrequent recombination (linkage disequilibrium) between the DR and DQ genes. Recombination events in the past, however, have occurred and generated distinct DR-DQ haplotypes, whose frequencies vary between races. DNA sequencing and oligonucleotide dot-blot analysis of class II genes from two race-specific haplotypes indicate that susceptibility to IDDM is closely linked to the DQA1 locus and suggest that both the DQB1 (ref. 7) and DQA1 genes contribute to disease predisposition.

Positive selection of Tac- (CD25) positive cells following T-cell activation. Use of immunomagnetic separation and implications for T-cell cloning

We have investigated if positive selection for cells expressing activation antigens, which appear on the cell surface during T-lymphocyte activation, could be used for cloning purposes. For this purpose, we used paramagnetic, monodisperse Dynabeads coated with anti-Tac monoclonal antibody, which recognizes CD25 (interleukin-2 receptor light chain). After the first 6-12 h of a primary response, depletion of Tac+ cells could largely abrogate the specific response. This indicated that the specifically responding cells were found among the Tac+ population. T-cell cloning was thus performed on Tac+ blasts positively selected after 18 h of a primary response, at day 6 of a primary response or during secondary stimulation, and gave a high percentage of specific clones. This method is thus a good alternative to established techniques.