HLA antigens of insulin-dependent diabetics

Monoclonal antibody definition of the DRB3 allele, HLA-Dw25

Monoclonal antibodies are powerful tools for analyzing HLA antigen polymorphism. We have investigated the serological and biochemical nature of the DRw52-related antigen defined by the monoclonal antibody NDS10. A detailed analysis of the population distribution of NDS10 reactivity revealed that the epitope was present on a subpopulation of DRw52 positive cells. A distinct pattern of reactivity was found within DR3 individuals: all of the B18,DR3 cells were NDS10 positive, whereas the A1,B8,DR3 cells were negative. All of the DR5(w11) cells and two of three DRw12 cells reacted with NDS10. NDS10 reactivity with DRw6 was not restricted to either of the serologically defined subtypes; three of 17 DRw13 and nine of 10 DRw14 cells were NDS10 positive. NDS10 was unreactive with all of the DRw8 cells tested. Two-dimensional gel analyses revealed that the NDS10 molecule precipitated from DR3, DR5(w11) and DRw6(w14) cell lines had an identical beta chain profile. These data indicate that NDS10 recognises the Dw25 allele of the DRw52 complex.

Variants of HLA-DRw52 defined by T lymphocyte clones

Polymorphism within the gene encoding the DRw52 allospecificity was studied with DRw52-specific proliferative T lymphocyte clones. Three clones, C6, E3 and ZUK16, were generated by intra-DRw52 priming in mixed lymphocyte culture and tested against an HLA-D homozygous reference cell panel. The reactivity of each clone could be specifically inhibited by anti-DR, but not anti-DQ or anti-DP, monoclonal antibodies. Clone C6 identified a DRw52 variant termed 52a that was predominantly expressed by HLA-B8,DR3+ and DRw13,Dw18+ cells. Clone E3 identified a variant termed 52b which was predominantly expressed by HLA-B18,DR3+,DRw11,Dw5+ and DRw14,Dw9+ cells. Clone ZUK16 identified a variant termed 52c which was predominantly expressed by DRw13,Dw19+ cells. The DRw52a, 52b and 52c variants correspond to the Dw24, Dw25 and Dw26 alleles defined by the WHO HLA 1987 Nomenclature Committee. Together, clones E3 and ZUK16 appeared to identify a fourth DRw52 variant termed 52d which was expressed by two cells, one DR3, Dw"3.3"+ and one DRw14,Dw"9.2"+. A fifth Drw52 variant termed 52e, expressed by a DRw13,Dw"OMW"+ cell, was suggested by the absence of reactivity with any of the three T cell clones. These data thus demonstrate the existence of three well-defined allelic variants of DRw52 and indicate that there are at least two additional variants. The recognition of these polymorphisms by alloreactive T cells provides one measure of their functional significance.

Correlations between polymorphisms at the DNA and at the protein level of DRw52 haplotypes, revealed with a variety of techniques

LB-Q1 and LB-Q4 are two subtypes of DRw52, defined by proliferative T-cell clones. These subtypes represent a polymorphism of the DR beta III gene. Similar subtypes of DRw52 can be defined by oligonucleotide typing, serology and RFLP analysis. In the present study we compared these typing techniques on a panel of 22 HLA-D homozygous, DRw52-positive typing cells. All typing techniques correlated very well. Three subtypes of DRw52 could be identified. Our results show that typing for cellularly defined structures can be done with a variety of noncellular techniques. This observation has important implications for matching in unrelated bone marrow transplantation and for disease association studies.

T-cell-defined DR4 subtypes as markers for type 1 diabetes

In most populations studied, HLA-DR4, a DRB1 (formerly DR beta I) allele, is increased in frequency among patients with insulin-dependent diabetes mellitus (IDDM). Using T-cells, one can distinguish five subtypes of DR4 (Dw4, Dw10, Dw13, Dw14, and Dw15). Two of these (Dw4 and Dw10) are IDDM-associated in the populations studied here. Therefore, Dw4 and Dw10 could be causative or merely markers for a linked diabetes allele. If they are causative, one might expect them to share some unique structural element or at least to associate consistently with IDDM in different populations. Published sequence data show no structural element unique to Dw4 and Dw10; moreover, the associations of these DR4-Dw subtypes with diabetes vary considerably in different populations. Thus the DRB1 locus probably cannot account for the DR4 association in IDDM. The strong linkage disequilibrium between IDDM and Dw4 and Dw10 suggests that the diabetes susceptibility locus should be in the vicinity of the DR region or the DQ region of the HLA complex. Alternative hypotheses are discussed, relating DR- and DQ-region alleles to IDDM. We further postulate that the evolutionary event that produced the Dw10 allele occurred on a Dw4 haplotype that happened to carry a diabetes susceptibility allele at another locus.

Two variants of DRw52, DR3, and DQw2 specificities distinguish two different DR3-bearing extended haplotypes

HLA-DR beta and DQ beta MHC antigens present on B-lymphoblastoid cell lines homozygous for either [HLA-B8,DR3,SC01] or [HLA-B18,DR3,F1C30] were studied by two-dimensional gel electrophoresis. Comparison of neuraminidase-treated DR proteins from these cells showed that DR3-bearing cells express two DR beta genes. However, one DR beta chain (beta a) is nonpolymorphic, whereas the other beta chain (beta b) is polymorphic. Two variants of DR beta (DR3 or DRw52) and two of DQ beta (DQw2) were found, with all the examples of each extended haplotype carrying only one of these sets of variants. The variants thus absolutely distinguished the two DR3-bearing extended haplotypes. These results support the hypothesis of extended haplotypes at the protein level, and demonstrate the fixity of alleles on them in the HLA-B-D/DR region.

Functional polymorphism of the HLA-DR beta III chain

Several clusters of class II HLA genes contribute to variation in human antigen-presenting capacity. In the HLA-DR cluster, most of the variation is due to the highly polymorphic DR beta I gene. Recent work by others has shown some nucleotide and implied amino acid sequence variation in DR beta III chains, but this variation is not known to be functionally significant. We show here that two proliferating human T-cell clones define three allelic variants of DR beta III (assignment to DR beta III based on blocking of proliferation by selected monoclonal antibodies). Thus, the DR beta III locus encodes at least three alleles that are distinguishable by human T cells and most probably contribute to the human antigen-presenting repertoire. The three DR beta III alleles subdivide the "supertypic" HLA antigen DRw52 into subtypes provisionally called DRw52.1-52.3. The DR3 haplotypes studied to date have been either DRw52.1 or 52.2; DR5 haplotypes have all (23 of 23) been 52.2; DRw6 haplotypes have included all three DRw52 subtypes, nearly half being 52.3. Our data, combined with other published data, imply that DRw8 must either have a fourth DRw52 subtype or be DR beta III null.

Inherited susceptibility to insulin-dependent diabetes is associated with HLA-DR1, while DR5 is protective

Of the HLA allelic associations with insulin-dependent diabetes (IDD) reported to date. DR3 and DR4 have been the most positive and DR2 the most negative. In 952 Caucasian proband patients reported here, only 57 or 6% had no DR3 or DR4 alleles. When these 57 patients were compared to 249 Caucasian controls similarly lacking DR3 and DR4 antigens, there were excesses of DR1 (P = 0.13) and DRW8 (P = 0.01) and deficiencies of DR2 (P = 0.03) and DR5 (P = 0.03) in the patient group. The most common phenotype in this group of patients was DR1/DR7 (12.3%). Only four DR-homozygous patients involving alleles other than DR3 and DR4 were found by genotyping, and all were DR1 homozygotes. Among 506 patients wuth DR3/DRX or DR4/DRX phenotypes, DR1 was more frequent (P = 0.001; Bonferronni P = 0.006), and DR2 (P = 0.001) and DR5 (P = 0.001) less frequent than 243 HLA-matched controls. Of 187 patients with a single DR3 and no DR4, DR1 was more frequent (P = 0.02), with DR2 (P = 0.001) and DR5 (P = 0.02) less frequent than 94 HLA DR-compatible controls. Among 319 patients with a single DR4 but no DR3, DR1 was again more frequent (P = 0.01) and DR2 (P = 0.001) and DR5 (P = 0.001) less frequent than 149 HLA-matched controls. We conclude that DR1 is an additional risk DR allele for IDD to that of DR3 and DR4, and DR5 an additional protective DR allele to that of DR2.

Molecular analysis distinguishes two HLA-DR3-bearing major histocompatibility complex extended haplotypes

We detected restriction fragment length polymorphisms that distinguish the extended haplotype HLA-B8,DR3,SCO1 from HLA-B18,DR3,F1C3O at the DR beta and DQ beta loci with five of seven restriction endonucleases used. One set of restriction fragments was always found on HLA-B8,DR3,SCO1 and associated with DRw52a, while the other was present on HLA-B18, DR3,F1C3O and correlated with DRw52b (the gene encoding the subtype of DRw52 associated with the BO1 or LB-Q1 antigen). Furthermore, using a full-length DQ beta gene probe, we found division in the DQw2 haplotype, in which DQw2a always associated with HLA-B8, DR3,SCO1, while DQw2b always occurred with HLA-B18,DR3,F1C3O. Our evidence thus indicates that serologically defined HLA-DR3, HLA-DRw52, and HLA-DQw2 are each produced by two structurally very different sets of genes, one set occurring in HLA-B8, DR3,SCO1, and the other in HLA-B18,DR3,F1C3O.

Susceptibility to IDDM is marked by MHC supratypes rather than individual alleles

107 patients with insulin-dependent diabetes mellitus (IDDM) were typed for HLA A, B, C-, and DR antigens, and for complement C4A, C4B, and Bf alleles, and the results were compared with those of a combined reference group of 332 appropriately matched healthy subjects. Supratypes (allelic combinations) were identified from the phenotype of each group, and it was shown that the frequency of several supratypes is increased in patients with IDDM, in particular supratypes (A1 Cw7) B8 C4AQ0 C4B1 BfS DR3 (P = 0.0001), (A30 Cw-) B18 C4A3 C4BQ0 BfF1 DR3 (P = 0.0003), (A2 Cw3) B62 C4AR C4B2.9 BfS DR4 (P = 0.0002), and three other supratypes including DR4. It was also shown that increases in the frequency of individual alleles are secondary to increases in supratype frequency. Moreover, supratypes appeared to interact; the presence of two relevant supratypes being particularly important. The absolute risk of IDDM was approximately 0.5 in subjects who were homozygous for B18 C4A3 C4BQ0 BfF1 DR3. We concluded that genetic susceptibility is best recognized by MHC supratypes rather than isolated alleles, and that supratype combinations make the identification of even greater disease risk possible.

A minor subset of HLA-DR3 haplotypes is preferentially increased in type 1 (insulin-dependent) diabetes

We have been using human T-lymphocyte clones specifically sensitized to detect leucocyte antigens of Type 1 (insulin-dependent) diabetic patients in the hope of detecting novel HLA antigens associated with Type 1 diabetes. We previously described two such clones which define a new class II HLA antigen, Boston-1 (BO1). BO1 is found mainly on cells of persons with particular HLA-DR antigens and, of potential significance for diabetes, BO1 identifies a distinctive subset of DR3 haplotypes. We report here that BO1+ DR3 haplotypes are overrepresented in Type 1 diabetes. That is, significantly more of the DR3-positive subjects are BO1-positive in the patient group (31%) than in the control group (8%), suggesting that a diabetes-susceptibility gene may be more common on the BO1+ than on the BO1- DR3 haplotypes. Alternative interpretations are also discussed.

HLA class II restriction repertoire of antigen-specific T cells. II. Evidence for a new restriction determinant associated with DRw52 and LB-Q1

We have studied the HLA class II restriction repertoire of antigen-specific T lymphoblasts (T-LB) in response to purified protein derivative (PPD) and tetanus toxoid (TET), presented by allogeneic antigen-presenting cells (APC). In 102 fully DR(1-w14) mismatched T-LB/APC combinations matching for DRw53 (MT3) had a significant influence on T-LB proliferation (p = 0.0005). Moreover, the supertypic specificity DRw52 (MT2) and LB-Q1 (a new class II determinant in strong linkage disequilibrium with DRw52) appeared to be markers for a new RD (p less than 0.0005). LB-Q1 was most strongly associated with this RD and among DRw52 identical T-LB/APC combinations additional LB-Q1 sharing significantly increased T-LB responsiveness (p = 0.02). DRw52- and LB-Q1-restricted responses could be inhibited by an anti-DRw52 and an anti-DR framework monoclonal antibody, indicating that DR(w52), LB-Q1, and the new RD are located at the same molecule.