Dissection of HLA class II haplotypes in HLA-DR4 homozygous individuals

Cloning of the bovine major histocompatibility complex class II genes

Class II genes of the bovine major histocompatibility complex (MHC) have been cloned from a genomic library. The library was constructed in the bacteriophage lambda vector EMBL3 and comprises approximately 10 times the equivalent of the haploid genome. Half the library was screened with the human DQA, DQB, DRA and DRB cDNA probes. Of the 100 positively hybridizing phage clones, 37 were eventually fully characterized and mapped by means of Southern blot analysis. The exons encoding the first, second and transmembrane domain of all different A and B genes were subcloned and mapped in more detail. These analyses showed that these 37 clones were derived from five different A and 10 different B genes. The hybridization studies indicate that we have cloned and mapped two DQA genes, one DRA gene, two other A genes, four DQB genes, three DRB genes and three other B genes. Since the library was made from a heterozygous animal, this would suggest that there are at least one DQA, one DRA one other undefined A, two DQB, two DRB and one or two other undefined B genes in the haploid genome of Holstein Friesian cattle.

Restriction fragment length polymorphism analysis of HLA haplotypes in families with type I diabetes mellitus

HLA Class II polymorphisms were analysed in 27 families with at least one Type I diabetic proband using Southern blotting technique according to 10th Histocompatibility Workshop Standards. The probes used were DRB, DQA1, DQB1 and DOB. We have studied 108 haplotypes and performed segregation analysis with HLA serology and restriction fragment length polymorphism (RFLP) data and compared "affected" with "non-affected" haplotypes (not inherited by IDDM patients). RFLPs correlated well with DR and DQ serology and detected additional polymorphisms. In particular, DQB polymorphism analysis showed segregation of the DQw3 splits with 88.5% of the DR4 affected haplotypes bearing the DQw3.2 split (now DQw8) and 11.5% the DQw3.1 split (now DQw7) while in the non-affected DR4 haplotypes 33.3% were DQw3.2 and 66.6% were DQw3.1. Haplotype analysis showed that DR4-DQw3.2 was in strong linkage with the U fragment (2.1 kb Taq I) of DQA2 (DX alpha) and with the L fragment (5.4 kb BamH I) of DOB. This study confirms previous observations of DQB polymorphisms in heterozygous IDDM patients, supports the protective effect of DQw3.1 (DQw7) against the development of the disease and demonstrates the importance of DQw3.2 (DQw8) for susceptibility to Type I diabetes.

HLA-DQ beta 3.1 allele is a determinant of susceptibility to DR4-associated rheumatoid arthritis

Rheumatoid arthritis is associated with HLA-DR4 in several ethnic groups. Since DR4 haplotypes encode a diverse array of class II molecules, it is of interest to characterize the nature of the primary association. We have examined molecular polymorphisms of HLA class II gene products expressed by normals and rheumatoid arthritis patients using monoclonal antibodies and two-dimensional electrophoresis. Most homozygous DR4 rheumatoid arthritis patients express DR beta 1 molecules associated with Dw4 or Dw14 mixed lymphocyte culture determinants. In Caucasoids, two DR4-linked DQw3-associated beta-chain alleles are defined by two-dimensional electrophoresis. These variants, designated DQ beta 3.1 and 3.2, are associated with the serologic determinants DQw7 and DQw8, respectively. A panel of 40 DR4-positive normals was also examined for nucleotide sequence polymorphisms associated with DQB3.1 and 3.2 genes using the polymerase chain reaction and specific oligonucleotide probes. At the DQ beta level the rheumatoid arthritis panel was distinguished by enrichment for the DQ beta 3.1 allele with 100% of patients positive for DQw7. Results presented here suggest that specific DQ beta alleles may modify the effect of HLA-DR4 beta 1 alleles in conferring susceptibility to rheumatoid arthritis in a phenotype-specific fashion.

Individuals with HLA-DR blank alleles display well-known DR-DQ RFLPs

We have characterized HLA-DRB, -DQA, and -DQB gene polymorphism in a large number of serologically DR blank haplotypes with the restriction enzymes Taq I, Bam HI, and Pvu II, with the aim of finding new RFLPs in the Caucasian population. Locus-specific RFLPs were combined for a definition of Taq I DR-DQ haplotypes. All observed DNA haplotypes could be found in a control group of 100 individuals, but with a different distribution. Serologically less well-defined specificities were over-represented in the blank group, in particular the DRw13-associated Taq I DR-DQ haplotype T-13.3. We conclude that the majority of DR blank haplotypes are probably closely related or identical to previously defined DR alleles. The extent of DR polymorphism in the Caucasian population seems to be well mapped, considering the extremely small proportion of rare Taq I DR-DQ haplotypes and lack of new patterns in this study.

Unambiguous typing for HLA-DQ TA10 and 2B3 specificities using specific oligonucleotide probes

Oligonucleotide probes specific for the serologically defined TA10 and 2B3 specificities were selected based on a comparison of the available HLA-DQ beta sequences. Panel and family segregation studies confirm a complete correlation between the reactivities of the selected probes and the TA10/IIB3 antibodies. The Glu residue at position 45 of the HLA-DQ beta chain is specific for the TA10 determinants, and a DQ beta Gly-Val-Tyr sequence is found at position 45-47 for all 2B3-positive DQ beta chains.

An HLA-DQ alpha allele identified at DNA and protein level is strongly associated with celiac disease

An HLA-DQ alpha cDNA probe showed upon hybridization a highly significant discrepancy between the RFLP of celiac disease patients and healthy controls. The 4.0-kb Bgl II restriction fragment was present in 97% of celiac disease patients (n = 30), compared to 56% in a healthy control population (n = 72) (RR = 14.9; p less than 0.0005). At the product level all celiac disease patients tested to date have one DQ alpha chain in common, designated HLA-DQ alpha 2.3, which is associated with the 4.0-kb Bgl II fragment. This HLA-DQ alpha allele identified at the DNA level and product level seems to be a better marker for genetic susceptibility to develop celiac disease than those available to date.

HLA-DR typing using restriction fragment length polymorphism (RFLP) with one enzyme and two probes

A panel of 43 homozygous and 36 heterozygous highly selected cells, representing the most common DR-specificities, were investigated with the DNA hybridization technique. By using a single restriction enzyme, TaqI, and two probes, DR beta and DQ alpha, it was possible to construct assignment criteria giving a reasonable definition of DR1, 3, 4, 5, 7 + w9, w8, w10 and w11. The criteria sometimes require that certain bands must not be present. Therefore, in certain genotypic combinations, the presence or absence of the particular specificity on one haplotype cannot be decided. This is a problem only for DR2 and DRw6, which for this reason cannot be assigned in about 1/3 to 1/4 of the cases. The association between RFLP assignment and serological assignment is not absolute, the correlation coefficients ranking from 0.62 to 1.0. In the case of false negative RFLP assignment, this may be due to genetic heterogeneity, as in the case of a DR2 individual who proved to be Dw12 and not Dw2 associated. It is often stated that interpretation of the RFLP pattern is particularly difficult in random or heterozygous individuals compared to proven homozygotes. This is not the case in the present study, where in fact correlation coefficients between RFLP and serologically determined DR specificities were higher in the heterozygotes (range 0.79-1.00).

Restriction fragment length polymorphisms and an HLA-DRw52-associated split

The restriction fragment length polymorphism technique, employing seven restriction endonucleases, and a DR-specific repeated element probe were used to study a large panel of homozygous typing cells in order to delineate haplotypic differences within the HLA-DRw52 supertype. Most of the restriction endonucleases revealed the presence of two allelic restriction fragment length polymorphisms correlating with and splitting the HLA-DRw52 supertypic specificity. One designated A, correlated with the HLA-DRw52 typing in HLA-DR5, HLA-DR3, (non-A1, B8), and some HLA-DRw6 haplotypes. The other, designated a, correlated with the HLA-DRw52 typing in HLA-DR5, HLA-DRw8, HLA-DR3 (A1, B8), and the remaining HLA-DRw6 haplotypes. The general applicability of these findings was validated in 47 HLA-typed laboratory controls.

Polymorphism and complexity of HLA-DR: evidence for intra-HLA-DR region crossing-over events

HLA-DR molecules were isolated from HLA-DR3, -5, and -w6 positive homozygous B-cell lines by immunoprecipitation with monoclonal antibodies and analyzed by gel electrophoretic techniques. DNA isolated from the same cell lines was digested with the restriction enzyme Taq I and hybridized with a DR beta full-length cDNA probe. We demonstrated that certain DR beta I alleles are found in combination with different DR beta III alleles as defined by Southern blotting, protein chemistry, a functional assay using purified protein derivative-specific T-cell lines, and, in one case, also alloreactive T-cell reagents. Our results indicate that within the family of HLA-DRw52-associated haplotypes DR beta chain genes may have been transferred from one haplotype to another. The implications of these findings are discussed.

Analysis of HLA-D micropolymorphism by a simple procedure: RNA oligonucleotide hybridization

Recent progress in the molecular genetics of HLA class II antigens has revealed the existence of multiple loci and of a large degree of polymorphism, with more individual alleles than was expected. An accurate detection and analysis of this extensive polymorphism is essential for optimal HLA typing for transplantation and for a reevaluation of HLA-disease association. Because of the limitations of the current typing methods, including restriction fragment length polymorphisms, we have proposed a DNA typing procedure based on hybridization with loci- and allele-specific oligonucleotides. Here we present a much simpler way of analyzing class II micropolymorphism down to the level of single nucleotide differences. RNA oligonucleotide typing (ROT) relies on RNA dot blots and requires 10-20 ml of blood. It is shown that with appropriate oligonucleotide probes, ROT can reliably and unambiguously identify any polymorphism at any of the HLA loci, including new alleles, not identified with previous methods. This illustrates the importance of oligonucleotide typing to optimize HLA matching, in particular for transplantation involving unrelated donors.

HLA-DR-DQ haplotypes defined by restriction fragment analysis. Correlation to serology

Through the analysis of RFLP (restriction fragment length polymorphism) of the HLA-DR beta, -DQ alpha, and -DQ beta genes from 70 serologically well-characterized individuals, we have established unique HLA-DR-DQ RFLP haplotypes correlating to all of the DR1-w14 specificities. The RFLP of DR beta, DQ alpha, and DQ beta genes is very high using the restriction enzyme TaqI and 21 DR-DQ RFLP haplotypes were defined with this restriction enzyme. Our analysis confirms the strong linkage disequilibrium between alleles in the DR and DQ loci. DR beta RFLP indicates a common ancestor for the DR alleles within either of the supertypic DRw52 and DRw53 specificities. The DQ beta gene shows a high degree of RFLP, and the RFLP alleles partly reflect the serologic DQw1-w3 specificities. The results presented here also demonstrate the heterogeneity of DRw6 (DRw13 and DRw14) associated haplotypes, and the DRw13 related Dw18 and Dw19 specificities were found to have distinct DR-DQ haplotypes. The DQw1 positive haplotypes DR1, 2, w10, w13, and w14 are related with regard to DQ alpha and DQ beta RFLPs and the DRw52 positive haplotypes DR3, w11, and w12, as well as the DRw53 positive haplotypes DR4, 7, and w9, are related with regard to DR beta and DQ alpha RFLPs. These findings indicate that polymorphic sequences around the DQ alpha gene are associated with DR beta and DQ beta polymorphism, which suggests a location of the DQ alpha gene between DR beta and DQ beta.

Molecular characterization by high-resolution isoelectric focusing of the products encoded by the class II region loci of the major histocompatibility complex in humans. I. DR and DQ gene variants

We describe a new approach to the analysis of the structural polymorphism of the DR beta, DQ alpha, and DQ beta polypeptide chains of human histocompatibility class II antigens. In comparison to conventional two-dimensional gel studies, this method provides sharper definition of the protein bands and side-by-side comparisons within the same gel, thereby permitting the detection of minor differences in the isoelectric points of the protein chains. Using this methodology we have analyzed the IEF polymorphism and the variability in the number of the DR beta chains encoded by different DR haplotypes. Twenty DR beta chain variants, which include the products of no less than two separate DR beta loci, have been thus far identified. Alleles at one of these loci are assumed to code for DR beta chains carrying the DR alloespecificities DR1, DR2, DR3, DR4, DR5, DRw6, DR7, and DR8. Alleles at a second DR beta locus encode DR beta chains that may be shared by serologically DR-different haplotypes and carry supertypic serologic specificities (i.e., DRw52 and DRw53). We also demonstrate here that the structural polymorphisms of the DQ alpha and DQ beta chains are more extensive than previously thought, report the characterization of 14 DQ beta variants, and define their relationship to the previously described DQw serologic specificities. In addition, we describe the class II haplotype associations observed for the different DR and DQ variants characterized.

RFLP of the HLA-DQ alpha region: a diallelic DX alpha polymorphism, not linked to DR and DQ specificities

HLA-DQ alpha DNA polymorphism was studied by Southern blot analysis in a panel of 117 individuals, consisting of 56 randomly selected and 61 HLA-DR homozygous individuals. Hybridizing fragments representing DQ alpha genes correlate with DR specificities owing to linkage disequilibrium between DQ and DR. Two fragments representing DX alpha genes were identified with the restriction enzymes PvuII and TaqI and a DQ alpha cDNA probe. The two fragments of PvuII-DQ alpha hybridization (a 7200 and a 7000 basepair fragment) and the two of TaqI-DQ alpha (2200 and 1900 basepairs) have an identical distribution in the panel, and reveal gene frequencies of 49.1% and 50.9%; they behave as alleles of the putative DX alpha locus. The panel study shows that the DX alpha fragments are not linked with the DR or DQ specificities but segregate along with HLA as shown in family studies.

Molecular localization of LB-Q1, a DRw52-like T-cell recognition epitope and identification at the genomic level of associated shared hybridizing fragments

In this paper we report on the molecular localization of LB-Q1, a supertypic HLA class II determinant which we previously identified by the use of proliferative T cells. The population distribution shows that each of the DRw52 associated specificities DR3, DR5, and DRw6 may occur with and without LB-Q1. DNA from nine DR3, six DR5, and 14 DRw6 homozygous B-cell lines were digested with the enzymes TaqI, EcoRI, and PvuII. Using a DR beta cDNA probe, shared hybridizing fragments were observed that correlate completely with the presence or absence of LB-Q1. T-cell recognition of LB-Q1 can be blocked with a monoclonal antibody (7.3.19.1) which in some haplotypes selectively reacts with the DR beta III chains, but cannot be blocked with a monoclonal antibody (I-LR2) reacting in those same haplotypes exclusively with DR beta I chains. Therefore, LB-Q1 maps to the DR beta III molecule. These data suggest the occurrence of relatively frequent previous recombinations between the two DR beta chain genes present in DRw52 haplotypes.

HLA DQ alpha and DQ beta restriction fragment length polymorphisms associated with Felty's syndrome and DR4-positive rheumatoid arthritis

HLA DQ alpha and DQ beta cDNA probes were used to study TaqI generated restriction fragment length polymorphisms (RFLPs) in DR4-positive patients with Felty's syndrome (FS), seropositive rheumatoid arthritis (RA), and in HLA-DR4 positive controls. The results of this analysis revealed two DQ beta RFLP patterns (DQ beta 3a and DQ beta 3b) associated with DR4, of which DQ beta 3b was found at significantly higher frequency in patients with FS (73%) or with RA (52%) than in DR4 controls (29%). Hind III generated RFLPs provide evidence that DQ beta 3b is in strong linkage disequilibrium with the gene encoding the serologically recognized epitope TA10. Results obtained using a DQ alpha chain probe revealed polymorphic differences between DQ alpha chain genes associated with different DR types, thereby providing a possible explanation for the lack of association between RA and other DR haplotypes in linkage disequilibrium with TA10. We conclude that both DQ alpha and DQ beta genes may be important in determining HLA-linked susceptibility to severe forms of RA.

Molecular diversity of HLA-DQ. DQ alpha and beta chain isoelectric point differences and their relation to serologically defined HLA-DQ allospecificities

HLA-DQ molecules were isolated from a panel of HLA-DR-DQ homozygous cell lines, partially of consanguineous origin, derived by the use of monoclonal antibody SPV-L3, and subsequently analyzed by gel electrophoretic techniques. It is demonstrated that both the DQ alpha and beta chain exhibit an extensive isoelectric point polymorphism. Within a panel of 29 B-cell lines tested, at least 5 distinct alpha and 6 distinct DQ beta chain gene products were observed. Of the 30 theoretically possible DQ alpha-beta dimers, only 10 could be identified within the panel: 5 different dimers are associated with the DQw1 allospecificity; HLA-DQw2 and -DQw3 are associated with 2 types of dimers, whereas another DQ alpha-beta combination was expressed by a cell line with a so-called DQ-blank specificity. The relation between the specificities 2B3 and TA10 appeared to be complicated as far as DQ beta chain isoelectric point differences are concerned: monoclonal antibody IIB3 seems to be reactive with four distinct DQ beta chain alleles whereas monoclonal antibody TA10 only reacted with one type of DQ beta chain. These results suggest that the polymorphic DQ alpha and beta chains may both contribute to the definition of the HLA-DQ allospecificity. A particular DQ beta chain was present in two types of HLA-DQw1 molecules, as well as in one type of HLA-DQw2 and -DQw3 (2B3 positive) molecule, and formed dimers with electrophoretic distinct DQ alpha chains. On the other hand, HLA-DQw2 molecules isolated from HLA-DR3-positive cells and one type of HLA-DQw3 (TA10 positive) molecule were found to be constructed of identical alpha chains but appeared to differ in the composition of their DQ beta chain gene products. The implications of these findings will be discussed.

Molecular cloning of a polymorphic DNA endonuclease fragment associates insulin-dependent diabetes mellitus with HLA-DQ

A BamHI 3.7-kilobase (kb) fragment detected by an HLA-DQ beta-chain complementary DNA (cDNA) probe and negatively associated with insulin-dependent diabetes mellitus (IDDM) was cloned and sequenced to localize the polymorphism to BamHI sites in intervening sequences of an HLA-DQ beta-chain gene. A probe of the first intervening sequence (IVS 1) showed the BamHI 3.7-kb fragment in 6 of 17 HLA-DR3/4 controls but in 0 of 13 DR-identical IDDM patients. All IDDM patients (13 of 13) had BamHI fragments of 12 and 4 kb, detected in 9 of 17 controls (P less than 0.02). The simple restriction fragment length polymorphism pattern of the IVS 1 probe was exploited by comparing 113 IDDM patients with 177 healthy controls to show increased prevalences in IDDM of the 12-kb (P less than 0.0001) and 4-kb (P less than 0.0001) fragments. In IDDM patients younger than 20 yr at onset, 98% were 12- and/or 4-kb positive, compared with 63% of controls (P less than 0.0001), giving a relative risk of 91.8 for individuals with both fragments. The 12-kb fragment was linked to HLA-DR4, and the 4-kb fragment to HLA-DR3. Both serologic markers were split and a non-DR3/non-DR4 IDDM patient was 4-kb positive. HLA-DQ seems therefore closer, than HLA-DR, to an IDDM susceptibility gene.

HLA class II DNA analysis by RFLP reveals novel class II polymorphism

Polymorphism of the HLA-D/DR region has been defined by serologic and cellular methods. Additionally, protein and DNA analyses not only confirmed and refined the definition of the established polymorphisms but also revealed further polymorphisms for which no serologic or cellular correlate are known (yet). To study these in more detail, we analyzed the banding patterns obtained from Southern blot hybridizations with DR beta and DQ alpha cDNA probes. Specific fragments reflecting already defined polymorphisms could be identified. A refined HLA-D/DR definition based upon the presence of DNA subtypes could be introduced. Fragments have also been identified that are associated with the DR/Dw specificities. Moreover, individuals with different DR types may also share fragments in hybridization assays. These shared hybridizing fragments (SHFs) are, for instance, found in individuals typed as DR4, DR5, DR7, and DRw8. In total, 20 SHFs were found using two restriction enzymes and the DR beta and DQ alpha cDNA probes. Some of these SHFs correlate with antigenic determinants defined by broad reacting alloantisera, such as DRw52, but for 14 of these SHFs, no serologic equivalent has been found so far. Thus, SHFs reflect a conservation at the DNA level of the HLA class II region, which suggests that the polymorphic class II genes may be more conserved than previously thought. The possible biologic implications of conserved sequences in the HLA class II genes will be discussed.

The HLA-Dw HAG specificity is defined by DR beta cDNA hybridization as a hybrid haplotype carrying DR5 and DRw6 determinants

The serological and cellular class II definition of HTC9W1802 HAG was difficult to establish. RFLP obtained with a DR beta cDNA probe indicated that HAG could be a hybrid haplotype composed of fragments characteristic for DR5 and DRw6 specificities.

Polymorphisms of DQ beta genes in HLA-DR4 haplotypes from healthy and diabetic individuals

The restriction fragment length polymorphism (RFLP) of DQ beta was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Bam HI, Bgl II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ beta associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4. a and DQ3.DR4.b, accounted for over 50% of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ beta. The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bgl II fragment and a 10.5 kb Bam HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ beta haplotype was significantly decreased in IDD-associated DR4 chromosomes (P = 0.04). These results suggest that the DQ3.DR4.b DQ beta allele may be protective for the development of IDD.

Oligonucleotide genotyping shows that alleles at the HLA-DR beta III locus of the DRw52 supertypic group segregate independently of known DR or Dw specificities

Using locus- and allele-specific oligonucleotide probes, we have studied the polymorphism of the HLA-DR beta III locus within the haplotypes of the DRw52 supertypic group. DNA from a number of homozygous typing cells typed for both Dw and DR was used. The DR beta III polymorphisms, DRw52a and DRw52b, do not segregate with Dw typing, or with DR typing, indicating that the determinants responsible for Dw-defined T-cell response and for DR haplotypic recognition are not encoded by the DR beta III locus. Hence, we can conclude that these DR specificities are encoded by the other functional DR locus, DR beta I, while the DR beta III locus encodes only the supertypic product.

An overview of the restriction fragment length polymorphism of the HLA-D region: its application to individual D-, DR- typing by computerized analyses

HLA-D/DR alleles as defined by cellular and serological typing can also be identified by biochemical methods. The Southern blot technique provides an additional typing facility which can be applied to DNA obtained from any source of nucleated cells. The polymorphism revealed by Southern blot analyses, the so-called restriction fragment length polymorphism (RFLP), depends upon the restriction enzyme and cDNA probes used. To identify HLA-DR specificities a protocol was developed based on the use of the results of southern blot analyses with several restriction enzymes and cDNA probes within a panel of HLA-D/DR homozygous cells representing the DR1 to DRw8 alleles. First, hybridizations with the 3' untranslated sequence of the DR beta cDNA probe, after digestion of the DNA with PvuII (PvuII-DR beta 3') allows the selective identification of DR1, DR2 and DRw8; DR3, DR5 and DRw6 are found as one group as well as DR4 and DR7 as another. Second, TaqI-DQ alpha hybridization allows the splitting of DRw6-Dw18, DRw6-Dw19 and DRw6-Dw9 from the DR3, DR5 and DRw6 group. The other alleles DR3, DR4, DR5, DRw6-Dw16 and DR7 are revealed by dehybridization and rehybridization of the blot with a DR beta cDNA probe. This protocol was used to test whether in a panel of 30 randomly chosen individuals the HLA-DR typing could be performed. The results were highly concordant to the serotyping. Furthermore by adding the Pst-DR beta and TaqI-DQ alpha RFLPs, most of the MLC defined Dw specificities could also be identified. An overview of the specific fragments described here has been summarized in matrices which can be used as references for DNA-typing in computerized analyses.

Reduced complexity of RFLP for HLA-DR typing by the use of a DR beta 3' cDNA probe

The polymorphism of the HLA system has been defined by alloantisera, monoclonal antibodies, MLC reactivity, protein chemistry and RFLP patterns in DNA analysis. Typing for the alleles of HLA-DR at the DNA level as an additional typing technique is useful since any nucleated cell can be used. Moreover, it is not known whether the additional polymorphism found at the DNA level in an unambiguous serotype is of functional importance and thus needs to be included in HLA-DR typing. A main problem in DNA typing is the interpretation of the complex patterns in Southern blot analysis, especially in heterozygous individuals. Therefore we constructed subprobes from full length DR beta, DQ alpha and DQ beta cDNA to reduce the number of hybridizing fragments while retaining the discriminating capacity. The clearest differences among DR alleles have been found using the restriction enzyme PvuII and the subprobe containing the 3' untranslated region of the DR beta probe. Although further characterization is necessary to be able to type at the DNA level, the simplified patterns facilitate DNA typing in heterozygous individuals for a number of haplotypes. Interestingly, the number of fragments thus obtained corresponds with the number of genes described for DR1 to DRw8 haplotypes. Based upon the finding of common hybridizing patterns in DR3, DR5 and DRw6 it may be concluded that DR3, DR5 and DRw6 have been evolved from a common ancestor. For the same reason DR4, DR7 and DRw9 may have evolved in an identical way.

HLA-DO polymorphism associated with resistance to type I diabetes detected with monoclonal antibodies, isoelectric point differences, and restriction fragment length polymorphism

A new HLA-DQ-related genetic system with two alleles, 2B3 and TA10, defined serologically by MAbs and alloantisera, showed an almost perfect correlation with charge differences on DQ beta molecules, as well as with two polymorphic DNA fragments hybridizing with a DQ beta probe and various restriction enzymes on a panel of 14 DR4+ homozygous typing cells. It was therefore concluded that the serologically defined alleles 2B3 and TA10 are coded by the DQ beta gene and situated on the HLA-DQ beta chain. This 2B3/TA10 polymorphism is independent of HLA-D and segregates with HLA in families. The TA10 allele appears to be a new marker for resistance to type I diabetes, which is independent from the known resistance marker DR2, whereas no association was observed between this DQ beta polymorphism and rheumatoid arthritis.

Polymorphisms within the HLA-DR3 haplotypes. I. HLA-DR polymorphisms detected at the protein and DNA levels are reflected by T-cell recognition

HLA-DR molecules were isolated from eight different HLA-DR3 homozygous B-cell lines by immunoprecipitation with monoclonal antibodies, and they were subsequently analyzed by two-dimensional gel electrophoresis. We found that HLA-DR3 homozygous B-cell lines of consanguineous origin express two types of HLA-DR molecules. One type of HLA-DR molecule was present in all the cell lines tested, whereas the second DR molecule appears to be polymorphic. DNA isolated from the different HLA-DR3 homozygous cell lines was studied by Southern blot analysis to determine whether any DR beta restriction fragment length polymorphism could be observed. Polymorphisms detected at both the product and genomic level have been compared to each other, and their relations to the serological (HLA-DR) and cellular (HLA-D and LB-Q1) typing data will be discussed.