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  • 1
    ISSN: 1420-9071
    Keywords: HLA ; haplotype ; disease ; diabetes ; arthritis ; Berger's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Extended HLA haplotypes frequencies were estimated from the HLA, C2, Bf and C4 phenotypes of 74 patients with non-insulin-dependent diabetes (NIDD), 92 with juvenile rheumatoid arthritis (JRA), 44 with Berger's disease (BD), 83 with insulin-dependent diabetes (IDD), and 140 healthy controls. The extended HLA haplotype B18 CF130 DR3 DQw2, which is common (around 10% phenotype frequency) in healthy Spaniards and in other populations of paleo-North African origin, was found to be significantly less frequent in NIDD, JRA and BD, whereas its frequency was normal in IDD (although DR3 DQw2 haplotypes were increased in the latter disease). These data support the existence of a common HLA-linked pathogeneic mechanism in NIDD, JRA and BD, and point to a genetic difference between IDD and NIDD at the HLA level. This effect is readily detectable in our population because the uncommon BfF1 allele marks that haplotype instead of the more common BfS, which marks B8 CS01 DR3 DQw2 in other Caucasians. Our results support the hypothesis of strong selective pressures operating at the HLA level to preserve extended HLA haplotypes with advantageous gene sets from dilution by crossing-over. Imbalanced incomplete haplotypes may give rise to inappropriate T-cell repertoire selection in the thymus and/or antigen handling in the periphery, and be partly responsible for the pathogenesis of certain HLA-linked diseases (i.e. NIDD, JRA, and BD).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: HLA-DR3 ; HLA-DR4 ; HLA-DO ; aetiologic fraction ; attributable risk ; human leucocyte antigens ; Type 1 (insulin-dependent) diabetes mellitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The question of HLA susceptibility to Type 1(insulin-dependent) diabetes mellitus remains unresolved. In the present study, 127 diabetic patients and 177 unrelated control subjects have been analysed for their class I and class II serological antigens, class II (DR, DQ) DNA restriction fragment length polymorphisms and DQA1 and B1 exon-2 nucleotide sequences and their corresponding amino acid residues. By using the aetiologic fraction (δ) as an almost absolute measure of the strongest linkage disequilibrium of an HLA marker to the putative Type 1 diabetes susceptibility locus, it has been found that the strength of association of the HLA markers may be quantified as follows: DR4 〈 DR3 〈 DR3 or DR4 〈 non-Aspartate 57 ßDQ and Arginine 52 αDQ 〈 Arginine 52 αDQ. Thus, molecular HLA-DQ markers appear to be more accurate as susceptibility markers than the classic serologically defined ones (DR3 and DR4); however, any effect of DQ markers disapears when non-DR3/DR4 individuals are considered, suggesting that DR factors (or others in between DQ and DR) are also important. In addition, a dominant non-Aspartate 57 ßDQ susceptibility theory does not hold (but a recessive one does) in our diabetic population (probably due to the high frequency of the protective DR7-non-Aspartate 57 ßDQ haplotypes); Arginine 52 aDQ is the best single HLA marker found in our population, both as a recessive or as a dominant one. Also there are 13 patients in our sample who bear neither Arginine 52 aDQ nor non-Aspartate 57 ßDQ susceptibility factors. On the other hand, a predominant Type 1 diabetes association of Spanish patients to the B18-DR3-Dw25 haplotype (and not to B8-DR3-Dw24) has been found; this distinctive association has also been recorded in adult systemic lupus patients and may reflect the existence of common pathogenetic HLA factors for both diseases present only in the B18-DR3-Dw25 haplotype in the Spanish population. These factors are probably placed at the non-coding regions which are different from the B8-DR3-Dw24 haplotype.
    Type of Medium: Electronic Resource
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