European journal of immunogenetics : official journal of the British Society for Histocompatibility and Immunogenetics最新文献

Exhaustive gene identification followed by assignment of the genes identified to corresponding loci is a key step in elucidating the physical structure of a multigene family. However, problems occur in this process because genes in a multigene family usually share a high degree of sequence identity and are highly polymorphic. To address these problems, an efficient population-based approach was developed. Using this approach, sequences in the human immunoglobulin VH4 family were amplified by PCR with family-specific primers. Denaturing gradient gel electrophoresis (DGGE) was used to separate the resulting sequences with either very similar or identical sizes and differing by as little as 1 base pair (bp). Eighteen distinct bands and 21 banding patterns were observed in the samples collected from 41 unrelated individuals. Of the 18 bands, 12 were polymorphic. No sample had all 18 bands. The estimated frequencies for the alleles represented by the 18 bands ranged from 1.2 to 100%. The 18 sequences differed from each other by 1-19 bases (0.7 to 13%) within the 145-146-bp amplified region. Sequences in eight bands (44%) were not reported previously. These results were used to assign the majority (14 out of 18) of the VH4 sequences to 10 loci. This PCR-DGGE method, in conjunction with a population-based assay, may also be used to study other multigene families including those involved in the development of the immune system.

HLA-associated relative risks of type 1 (insulin-dependent) diabetes mellitus were analysed in population-based Swedish patients and controls aged 0-34 years. The age dependence of HLA-associated relative risks was assessed by likelihood ratio tests of regression parameters in separate logistic regression models for each HLA category. The analyses demonstrated an attenuation with increasing age at onset in the relative risk for the positively associated DQB1*0201-A1*0502/B1*0302-A1*0301 (DQ2/8) genotype (P = 0.02) and the negatively associated DQB1*0602-A1*0102 (DQ6.2) haplotype (P = 0.004). At birth, DQ6.2-positive individuals had an estimated relative risk of 0.03, but this increased to 1.1 at age 35 years. Relative risks for individuals with DQ genotype 8/8 or 8/X or DQ genotype 2/2 or 2/X, where X is any DQ haplotype other than 2, 8 or 6.2, were not significantly age-dependent. An exploratory analysis of DQ haplotypes other than 2, 8 and 6.2 suggested that the risk of type 1 diabetes increases with age for DQB1*0604-A1*0102 (DQ6.4) and that the peak risk for the negatively associated DQB1*0301-A1*0501 haplotype is at age 18 years. There was also weak evidence that the risk for DQB1*0303-A1*0301 (DQ9), which has a positive association in the Japanese population, may decrease with age. We speculate that HLA-DQ alleles have a significant effect on the rate of beta cell destruction, which is accelerated in DQ2/8-positive individuals and inhibited, but not completely blocked, in DQ6.2-positive individuals.

There is evidence for a link between MHC and squamous cell carcinoma of the cervix (SCCC), and different patterns of association in different patient cohorts have been reported. To investigate this subject in the Spanish population, HLA class I, -II serotypings and HLA-DQB1 oligogenotypings of 142 patients and 138 healthy sex-age-matched controls were performed. Comparative analysis of the DR2-DQ3-stratified phenotypes demonstrated a strong association between DR2 and DQ3 in SCCC (Pc9 < 7 x 10(-8)). However, no interaction was observed between the two HLA factors, which seem to confer two weak and independent risks. Thus, phenotypes with DR2 and/or DQ3 (patients, 79%, controls, 60%; P < 5 x 10(-4)) were over-represented, while the less common DR2/DQ3-negative phenotypes with the HLA class I A2 antigen were found to confer the highest risk (EF = 62%, Pc84 < 1 x 10(-2)) of SCCC. Comparative analysis of allele frequencies revealed two weakly significant increases, one for DQB1*0301 (P < 1 x 10(-2)) in low-moderate dysplasias (CINI,II), and the other for DQB1*0402 (P < 3 x 10(-2)) in severe dysplasia in situ (CINIII/CIS), and a trend for an increase of DQB1*0302 among CINIII/CIS and invasive SCCC (ISCCC). With regard to DQB1 genes encoding the DR2-associated DQ serotypes, there was no significant deviation in patients. In contrast, the frequency of DQB1*0603 was found to be weakly decreased in CINI,II (P < 5 x 10(-2)) and ISCCC (P < 3 x 10(-2)), indicating a protective effect for this DR13 serotype-associated allele. No significant association could be shown between HLA and HPV infective status. However, there is circumstantial evidence that HPV-infected lesions may have been misassigned in some cases, and the sample size was small, so a role for DQB alleles in modifying the course of HPV-induced diseases cannot be excluded. The observations in this study suggest A2, DR2, DQB1*0301, DQB1*0402 and DQB1*0603 as independent factors associated with SCCC and as relevant targets in HLA-restricted peptide presentation. Our results are consistent with the theory that HLA loci may have different contributions in susceptibility and resistance to low-moderate dysplasias, CIS and invasive SCCC.

Several recently reported HLA-DPB1 alleles have only been identified in a single family or individuals and are of unknown distribution world-wide. Many new DPB1 alleles appear to arise as a result of gene conversion-like events, which may localize variant DPB1 alleles to the population in which they were first identified. Using two SSOP-based typing methods in parallel, we have identified HLA-DPB1*6301 in an individual from rural Cameroon which has previously only been reported in a family of Mexican-American origin. The presence of DPB1*6301 was confirmed by sequence-based typing of exon 2.