Class III gene rearrangements in Thai/Chinese supratypes containing null or defective C4 alleles

Association of the complement allele C4AQ0 with primary Sjögren's syndrome in Japanese patients

We studied allotypes of the fourth component of complement (C4) and factor B in 76 patients with Sjögren's syndrome (SS) and in 63 normal subjects. C4A-null (C4AQ0) was found in 10 of 28 patients who had primary SS, compared with 1 of 63 control subjects (P less than 0.005). In contrast, no significant difference in the frequency of any C4 allotype was observed between patients with secondary SS and control subjects. An association of HLA-DRw53 with primary SS in Japanese patients has been reported. Since there is no linkage disequilibrium between DRw53 and C4AQ0, it is possible that at least 2 genes in the major histocompatibility complex may determine susceptibility to the development of primary SS in the Japanese population.

Characterization of MHC ancestral haplotypes associated with insulin-dependent diabetes mellitus: evidence for involvement of non-HLA genes

Insulin-dependent diabetes mellitus (IDDM) is associated with several DR3- or DR4-containing ancestral haplotypes (AHs). Using pulsed field gel electrophoresis (PFGE), long range maps of 35 haplotypes have been derived and classified. Two diabetogenic DR3-containing AHs (8.1 and 18.2) possess deletions in the central non-HLA region; these have not been found on non-diabetogenic AHs tested to date. In addition, 8.1 and 18.2 also carry other deletions not found on other AHs. Three DR4 containing AH lack a Not I site, which may imply excision of an unidentified gene. These and other data suggest that deletions may be relevant to the pathogenesis of autoimmune disease, possibly through causing quantitative differences in autoimmune responses involved in IDDM. The MHC contains several regions of potential interest in relation to susceptibility to IDDM; these may explain the association with only certain DR3- and DR4-carrying AH and DR3,4 heterozygosity in terms of cis and trans interactions. On the other hand, the class II region may be particularly important in protection.

Extensive deletions and insertions in different MHC supratypes detected by pusled field gel electrophoresis

The genomic organization of the human MHC was examined in multiple examples of six different supratypes using pulsed field electrophoresis (PFGE) after digestion of genomic DNA with infrequency cutting restriction endonucleases. Differences in restriction fragment length and band intensity were shown to be specific for each supratype. Mapping of the MHC revealed that each supratype contains previously undescribed deletions and insertions between HLA B and DQ regions.

Coexistence of an MHC chromosomal segment marked by HLA B17,BfS,C4A6,B1,DR7, and DQw9 in different ethnic groups

Previously we have shown that the supratype HLA B17 BfS C4A6 B1 DR7 (17 6 1 7) carrying a C4/Bgl II RFLP correlating with C4A6 coexists in whites and Thai/Chinese. Using conventional and PFGE/Southern blotting with class II, class III, and TNF probes as well as serologic DQ subtyping, we have extended these comparisons and now report that four examples each of white and Oriental 17 6 1 7 bear DQw9, as well as an approximately 10kb fragment hybridizing with a DR beta probe following digestion of genomic DNA with Hind III. Furthermore, Oriental and white 17 6 1 7 share a genomic insertion of some 70kb close to the class II region. These data suggest that 17 6 1 7 may mark a highly conserved chromosomal segment which provides new insights into the biology and evolution of the major histocompatibility complex.