Faculty Bibliography

Mixed lymphocyte typing provides an exquisitely sensitive means of detecting the polymorphism of HLA class II molecules. By using this technique, the differences between divergent human populations become apparent. This study describes a DR1 haplotype commonly present in the American black population. Unlike the Northern European population in which almost all DR1 individuals are DQw1 and type as Dw1 by using mixed lymphocyte typing, approximately 50% of DR1, DQw1 positive American blacks express an undefined Dw specificity. The DR beta polypeptide encoded by a DR1,Dw-cell differs from a previously described DR1,Dw1 beta sequence by two amino acid replacements at positions 85 and 86 in the first domain. One silent nucleotide substitution has also been identified. DQ alpha and beta first domain cDNA sequences from this haplotype are identical with previously described DQ sequences from a DR1,Dw1 cell. This relatively minor change in amino acid sequence of the DR molecule appears to produce the undefined HLA-D specificity in this haplotype. The variant DR1 sequence is shared with a DR beta-chain from the DR2,DwMN2 haplotype suggesting that a gene conversion-like mechanism has generated this difference

The nucleotide and inferred amino acid sequence of a DRw10 beta chain was obtained from cDNA clones isolated from a DR1, DRw10 heterozygous cell line. The sequence of this beta chain gene was distinctive, differing from those of all other defined DR types. The DRw10 beta chain gene was shown by transfection experiments to encode a polymorphic epitope recognized by mAb 109d6 that is also encoded by the DRw53 beta 2 chain gene. Comparison of the nucleotide sequence of both genes revealed that their third D regions (amino acids 67 to 73) were identical. This suggested first that the 109d6 epitope could be encoded by residues of this region, and second, that a putative gene conversion event transferred this sequence along with the information encoding the 109d6 epitope from a donor gene such as DRw53 beta 2. The sequence of the DRw10 beta chain gene was observed to be identical to that of clone pII beta 4 derived from the non-DR3 haplotype in the Raji cell line, which was also demonstrated to express the determinant recognized by antibody 109d6, suggesting that the typing of this cell line is HLA-DR3/DRw10. No evidence was found for the existence of a DR beta 2 chain gene product encoded by the DRw10 haplotype. The DRw10 haplotype was of particular interest because it was present along with a DR1 haplotype in the propositus who had rheumatoid arthritis, and was shared by the DR4-positive son of the propositus, who also had rheumatoid arthritis. This raised the possibility that the DRw10 haplotype, and most probably one or more specific conformations encoded by the DR beta chain, are involved in the definition of the disease susceptibility phenotype

The polymorphism of HLA class II molecules in man is particularly evident when comparisons between population groups are made. This study describes a DR3 haplotype commonly present in the American black population. Unlike the Northern European population in which almost all DR3 individuals are DQw2, approximately 50% of DR3-positive American blacks express a serologically undefined DQ allelic product. DNA restriction fragment analysis with the use of several unrelated individuals and an informative family has allowed us to identify unique DQ alpha- and beta-fragments associated with the DR3, DQw- haplotype. Based on fragment size, the DQ alpha genes of the DR3, DQw- and DRw8, DQw- haplotypes are similar as are the DQ beta genes of DR3, DQw-; DRw8, DQw-; and DR4, DQw- haplotypes. In addition, a DX beta gene polymorphism has been identified which is associated with some DR3 haplotypes including the American black DR3, DQw- haplotype. cDNA sequence analysis has revealed a DQw2-like alpha gene and a DQ beta gene which is similar to that previously described for a DR4, DQw- haplotype. It is postulated that recombination between DQ alpha and DQ beta genes and between the DQ and DX subregions has generated the various DR3 haplotypes and has played an important role in creating diversity in the HLA-D region.

This is an interpretive review of recent immunologic and molecular biologic data concerning the molecular basis of susceptibility to rheumatoid arthritis. The central point of view was taken that the major histocompatibility complex (MHC) class II molecules encoding disease susceptibility function in an immune recognition event involving an antigen 'X' that currently eludes characterization. The problem of understanding the meaning of the association of susceptibility with diverse MHC alleles such as DR4 (Dw4 and Dw14), DR1, and DRw10 is approached by detailed biochemical analysis that led to the identification of common stretches of amino acid sequence, presumably encoding conformationally equivalent structures. Non-classic MHC polymorphisms related to disease susceptibility but not associated with particular alleles such as identified by Ab 109d6 proved especially valuable in suggesting new directions for attempting to understand the significance of these associations. Consideration is given to the possibility that a family of either slightly different or identical conformations encoded in either cis or trans cumulatively confer the liability to develop rheumatoid arthritis, and implying a highly non-classic mode of inheritance. The available data do not permit a distinction between the possibilities that an antigen 'X' was being presented to T cells or whether the distinctive conformations of the MHC class II molecule serve the same role as antigen 'X' but are directly recognized by T cells. However, with additional data, some limited insight should be able to be inferred about the nature of an antigen 'X' that specifically binds to the MHC conformation with a complementary interaction. It seems reasonable to consider the pathogenesis of rheumatoid arthritis as a typical immune response resulting from a simple immune recognition event of a single antigenic molecule

An interpretive summary of recent immunologic and molecular biologic data concerning the molecular basis of susceptibility of rheumatoid arthritis will be presented. The central point of view is taken that the MHC class II molecules encoding disease susceptibility function in a specific immune recognition event. This could involve an antigen 'X' that currently eludes characterization or be directed to polymorphic determinants on the MHC molecule itself. The problem of understanding the meaning of the association of susceptibility to rheumatoid arthritis with diverse MHC alleles such as DR4 (Dw4 and Dw14) and DR1 is approached by detailed biochemical analysis that led to the identification of common stretches of amino acid sequence, presumably encoding conformationally equivalent structures. The sequence shared by the otherwise unrelated DR1 and DR4 haplotypes from residue 67 in the DR a chain that appears to confer susceptibility is Leu-X-X-Gln-Arg/Lys. Non-classic MHC polymorphisms related to disease susceptibility but not associated with particular alleles such as identified by Ab109d6 prove especially valuable in suggesting new directions for attempting to understand the significance of these associations. Consideration is given to the possibility that a family of either slightly different or identical conformations encoded in either cis or trans cumulatively confer the liability to develop rheumatoid arthritis. This implies a highly non-classic mode of inheritance. It seems reasonable to consider the pathogenesis of rheumatoid arthritis as evolving from a typical immune response based on a simple immune recognition event directed to a single antigen

Two major DR7 haplotypes have been defined on the basis of serologic typing: those that type as DQw2 and others that type as DQw3. In order to define the molecular basis for these serologic differences we have isolated and sequenced DQ alpha, DR beta I, and DQ beta cDNA clones from both representative haplotypes. These studies reveal that although the DQ alpha and DR beta I genes of both haplotypes are identical, the DQ beta genes are very different. These data suggest that the serologic differences of these two DR7 haplotypes are the result of a recombinational event that occurred between the DQ alpha and DQ beta genes. In addition, they emphasize the role of DQ recombination in generating 'hybrid' HLA-DQ heterodimers

We have isolated and sequenced cDNA clones corresponding to the polymorphic alpha and beta chains encoded by the DR and DQ subregions of two HLA-DR4 haplotypes, LD'KT2' and LD'TAS'. These two haplotypes are distinguished on the basis of mixed lymphocyte culture typing. The data indicate that the designation of LD'TAS' as a distinct subtype from Dw13 is very likely due to amino acid differences in the DQ beta chain. In contrast, LD'KT2' differs from TAS and Dw13 by a single amino acid substitution at position 37 of the DR beta 1 chain. The functional and evolutionary significance of these polymorphisms is discussed

Tryptic peptide map analysis by high-pressure liquid chromatography of DR4- associated DR beta chains revealed limited structural variation within DR beta polypeptides. Comparison of 3H-leucine-labelled tryptic peptide maps of Dw4 and Dw14 homozygous cells identified distinct peaks corresponding to Dw4 and Dw14-associated DR beta polypeptides. HPLC analysis of cell line 256, heterozygous for two DR4-related specificities, Dw4 and Dw14, displayed both peptides, corresponding to the variable Dw4 and Dw14 chromatograms. This observation was confirmed using a deletion mutant cell line derived from 256 lacking Dw4-associated class II genes. The observed peptide variation correlated precisely with predicted nucleotide-derived amino acid sequences implicating amino acids 66-71 of the DR beta chain as contributing to HLA-D structural and functional polymorphisms