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

Immunogenetic associations of scleroderma-related antinuclear antibodies

Patients selected for the presence of scleroderma-related antibodies (anti-DNA-topoisomerase I [anti-topo I; n = 43], anticentromere antibody [ACA; n = 63], or anti-Pm-Scl [n = 12]) were studied for class I and class II major histocompatibility complex antigens, as well as for Gm and Km allotypes. Anti-topo I was associated with HLA-DR5 (70% of patients versus 30.6% of controls; Pcorr = 0.0018, relative risk [RR] = 5.3). All patients with anti-Pm-Scl were positive for HLA-DR3 (versus 23.5% of controls; Pcorr less than 0.001); 6 of these patients were DR3/4 heterozygous (50% versus 3.5% of controls; Pcorr less than 0.001, RR = 27.3). Patients with ACA were frequently positive for HLA-DR1, DR4, or DRw8, with 73.7% demonstrating at least 1 of these alleles (versus 41.2% of controls; Pcorr = 0.0152, RR = 4.0). This group of ACA-positive patients who had DR1, DR4, and/or DRw8 consisted mainly of a subgroup of patients with rheumatoid arthritis. We conclude that different class II major histocompatibility complex antigens influence the formation of anti-topo I and anti-Pm-Scl. Important clinical differences between these patient groups and the immunogenetic heterogeneity support the notion of different antibody-defined scleroderma subsets.

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.

A combination of HLA-DQ beta Asp57-negative and HLA DQ alpha Arg52 confers susceptibility to insulin-dependent diabetes mellitus

Family and population studies indicate that predisposition to insulin-dependent (type I) diabetes mellitus (IDDM) is polygenic. It has been shown that the absence of the aspartic acid in position 57 (Asp57) of the DQ beta chain is positively correlated to IDDM. However, Asp57-negative haplotypes do not always confer susceptibility and conversely, some Asp57-positive haplotypes seem to be disease associated. It has been suggested that other HLA class II sequences, probably belonging to the HLA DQA1 gene, confer susceptibility to IDDM. This report, based on extensive oligonucleotide dot blot hybridization of PCR-amplified DQA1 and DQB1 genes, reinforces the importance of the Asp57-negative DQ beta chain, but also introduces the possibility that a DQ alpha chain bearing an arginine in position 52 (Arg52) confers susceptibility to IDDM. A molecular model of susceptibility to IDDM is proposed. This model strongly suggests that the disease susceptibility correlates quantitatively with the expression at the cell surface of a heterodimer, composed of a DQ alpha-chain bearing an Arg52 and a DQ beta chain lacking an Asp57. In view of the respective positions of the two residues and their charge, we might anticipate that both residues DQ beta Asp57 and DQ alpha Arg52 are critical for modulation of susceptibility, presumably via viral-antigenic peptide and/or autoantigen presentation.

Aspartic acid at position 57 of the HLA-DQ beta chain is not protective against insulin-dependent diabetes mellitus in Japanese people

Insulin-dependent diabetes mellitus (IDDM) in Caucasians is closely associated with the HLA-DQ gene, especially the residue 57 of the DQ beta chain. Aspartic acid at this position provides protection against IDDM, and substitution of this residue by alanine, valine or serine increases susceptibility to IDDM. To determine whether this is a common feature of IDDM in different ethnic groups, we studied DQB1 DNA in Japanese patients with IDDM by polymerase chain reaction and non-radioactive restriction site analysis. In contrast to Caucasian patients with IDDM, most Japanese patients with IDDM possessed at least one aspartic acid at position 57 of DQ beta. This finding strongly suggests that aspartic acid at position 57 of DQ beta does not protect the Japanese from IDDM.

Analysis of MHC class II DNA polymorphisms in Negroid subjects

Study of the MHC class II region is complicated by strong linkage disequilibrium between DR and DQ. Comparison of DR-DQ haplotypes between different races partly resolves this problem. We present the results of an analysis of DRB, DQA and DQB restriction fragment length polymorphisms in serologically DR-typed subjects of Negroid origin. Clearly distinguishable DRB RFLPs were observed for DR1,2,5,7 and w8. DR4,9 and w10 were uncommon in this group. DR3 was associated with two extended haplotypes, one characterised by the DQw4 allele, the other by the DQw2 allele. A recently recognised DQB RFLP (DQB 2c) was associated with DR7 and also occurred on DR5 and DR9 haplotypes. Both DR5 and DRw6 were heterogeneous in their DR-DQ relationships. Negroid subjects exhibit DR-DQ relationships distinct from other races. These provide scope for further study of MHC class II associations with disease.

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-DP, -DQ and -DR RFLP types in south Indian insulin-dependent diabetes mellitus patients

The frequencies of HLA-DP, DQ and DR RFLP types are compared between insulin-dependent diabetes mellitus (IDDM) patients and healthy controls in the South Indian population. There are no significant differences in the frequencies of any of the DPA. DPB haplotypes, when allowance is made for multiple comparisons. The individual frequencies of two novel alleles, designated "DPA*B" and "DPB*B", however, are significantly higher in controls than in patients, suggesting that these alleles are protective against IDDM. A negative association with DRw15 (DR2). Dw12 is also observed. The positive association with DPw3/6 RFLPs previously observed in White Australians is not present in South Indians. This difference may be due either to undetected heterogeneity within allelic classes or to different linkage disequilibrium patterns between the populations.

HLA class II polymorphism and genetic susceptibility to insulin-dependent diabetes mellitus

As we have discussed previously (Horn et al. 1988a; Erlich et al. 1989b; Horn et al. 1988b), there are no unique class II sequences associated with IDDM, which suggests that "normal" class II alleles confer susceptibility. Given the estimates of concordance--under 50% of monozygotic twins and approximately 15% (Tattersol, Pyle 1972 and Thomson 1988) for HLA-identical sibs--, it is not surprising that some unaffected individuals contain putative susceptibility alleles. Perhaps some environmental "triggering" agent, such as viral infection (Yoon, this volume), is required for the disease to develop in susceptible individuals. Other non-MHC linked genes which contribute to susceptibility may account for the difference in concordance rates for monozygotic twins and for HLA-identical sibs. In the nonobese diabetic mouse and the BB rat models for IDDM, non-MHC susceptibility loci have been identified and mapped (Hattori et al. 1986; Colle et al. 1981), but in humans the analysis of non-MHC candidate loci (i.e., the T cell receptor) has thus far failed to reveal any other susceptibility loci. In general, the HLA-linked genetic susceptibility to IDDM, as well as to other autoimmune diseases, appears to be associated with specific combinations of class II epitopes (e.g., alleles, haplotypes, or genotypes) rather than with specific individual residues or epitopes. Understanding the role of these predisposing sequences will require structural analysis of the class II molecules as well as in vitro and in vivo functional studies of interactions with putative autoantigens and T cell receptors. In the meantime, DNA typing offers the potential for identifying individuals at high risk for IDDM.

Glycosuria and insulitis in NOD mice expressing the HLA-DQw6 molecule

To investigate HLA-linked genes controlling the susceptibility and resistance to insulin dependent diabetes mellitus (IDDM), HLA-DQ alleles of 45 Japanese patients with IDDM were analysed, using sequence specific oligonucleotide (SSO). DQA1*0301 and DQB1*04 were positively associated (R.R = 6.6, Pc less than 0.05 and R.R. = 4.7 Pc less than 0.01) and DQA1*0103 and DQB1*0104 were negatively associated (R.R. = 0.2, Pc less than 0.01) with IDDM. DQA1*0103 and DQB1*0104 were in strong linkage disequilibrium to encode for DQw6 molecule. Therefore, in a Japanese population, the DQw6 molecule seems to control the resistance to IDDM. To determine whether or not the DQw6 molecule itself can protect against glycosuria and insulitis in NOD mice, these animals were mated with HLA-DQw6 transgenic-C57BL/6 mice (DQw6-B6) and the F1 progeny expressing the DQw6 molecule were backcrossed with NOD mice. Eighty-five female backcross progenies were classified into four groups, according to the MHC classII phenotype; I-ANOD/I-ANOD DQw6(-), I-ANOD/I-ANOD DQw6(+), I-ANOD/I-Ab DQw6(-) and I-ANOD/I-Ab DQw6(+). At the age of 16 weeks, 9.1% of the DQw6(-) I-Ab(-) mice had a glycosuria whereas none of the DQw6(+) I-Ab(-) mice had a glycosuria. At the age of 30 weeks 13.6% of the DQw6(-) I-Ab(-) mice had a glycosuria and 7.7% of the DQw6(+) I-Ab(-) mice had a glycosuria. Histological examinations of the pancreas were performed in the 30 week old mice or after the development of glycosuria.(ABSTRACT TRUNCATED AT 250 WORDS)

DQA1 restriction fragment length polymorphisms and insulin-dependent diabetes mellitus: a BglII fragment labels a subset of B8,DR3 haplotypes uniquely associated with insulin-dependent diabetes mellitus

Class II restriction fragment length polymorphism studies of 38 pedigrees with multiple cases of insulin-dependent diabetes mellitus revealed the existence of a DQA1-related polymorphism that distinguishes two kinds of HLA-B8,DR3 haplotypes. One of these, characterized by the presence of DQA1-BglII 7.20 kb, was present in all 14 examples inherited by patients and in 6 of the 12 B8,DR3 haplotypes not so inherited. The apparently complete association between the presence of this fragment and the "affected" status of B8,DR3 haplotypes (p = 0.004) was confirmed in a separate group of 26 simplex pedigrees selected for the presence of this haplotype in the respective probands (combined p less than 0.0001).

The amino acid at position 57 of the HLA-DQ beta chain and susceptibility to develop insulin-dependent diabetes mellitus

In Caucasoids HLA-DQB1 genes encoding amino acids other than aspartic acid at position 57 of the DQ beta chain (non-Asp-57) are associated with susceptibility to develop insulin-dependent diabetes mellitus (IDDM), while resistance is associated with aspartic acid at this residue (Asp-57). Following amplification of genomic DNA by the polymerase chain reaction, the DQB1 alleles of 87 random Norwegian IDDM patients and 187 healthy controls were investigated with 11 different sequence-specific oligonucleotide probes. Of these patients 82% carried DQB1 alleles encoding non-Asp-57 at both of their DQ beta chains, compared to 27% of the controls (relative risk = 12.2, p less than 0.0001). Sixteen percent of the patients (versus 51% of the controls) were heterozygous Asp-57/non-Asp-57. Two percent of the patients (22% of the controls) were apparently Asp-57 homozygous. The results demonstrate that non-Asp-57 DQ beta chains are associated with susceptibility to develop IDDM but also indicate that the protection associated with DQ beta Asp-57 may not be as dominant as reported by others.

HLA-DR and -DQ antigens in malnutrition-related diabetes mellitus in Ethiopians: a clue to its etiology?

Thirty Ethiopian malnutrition-related diabetes mellitus (MRDM) patients were HLA typed and their HLA antigen frequencies were compared to those of 31 previously typed insulin-dependent diabetes mellitus (IDDM) patients and to 84 controls from the same ethnic background. In comparison to controls, a striking association between MRDM and HLA-DR3 (X2 = 15.15, p = 0.0001) was observed, whereas the frequency of HLA-DR4 was non-significantly increased (RR = 1.72). The frequency of DR2, DQw1, and DQw6 was decreased among MRDM. In comparison to IDDM that is associated with both DR3 and DR4 in this population, MRDM showed no significant differences in HLA class II antigens frequencies. Therefore, the genetic basis of susceptibility to MRDM and IDMM in Ethiopia is at least partially identical.

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.

Aspartic acid at position 57 of DQ beta chain does not protect against type 1 (insulin-dependent) diabetes mellitus in Japanese subjects

HLA DQ beta chain, in particular amino acid at position 57, has been reported to contribute to susceptibility and resistance to Type 1 (insulin-dependent) diabetes mellitus in Caucasians. Resistance has been proposed to be conferred by aspartic acid at this position. To ascertain the association of HLA DQ beta and DR beta genes with Type 1 diabetes in Japanese subjects, ten Japanese Type 1 diabetic patients were investigated at DNA level. Genomic DNA was amplified by polymerase chain reaction, and dot blot analysis was carried out using the amplified DNA with allele specific oligonucleotide probes. All patients had aspartic acid at position 57 of at least one of their two DQ beta chains, and there was no significant difference of amino acids at the same position of DR beta chain in patients compared to control subjects. These data indicate that the protective role of aspartic acid at position 57 of DQ beta chain is less significant in Japanese compared with Caucasian subjects.

The immunogenetics of insulin-dependent (Type I) diabetes

Insulin-dependent diabetes develops when a genetically predisposed individual is exposed to an as-yet-unknown environmental insult. A major part of genetic susceptibility to the disorder is encoded close to or within the HLA-DQ region, but non-HLA-linked genes are also implicated.