Molecular typing of HLA class II antigens in a Säo Paulo population

Uma análise do perfil dos antígenos HLA de classe II numa amostra da populaçäo de Säo Paulo é descrita neste trabalho. Os dados foram obtidos através de técnicas de amplificaçäo gênica utilizando-se iniciadores seqüências-específicos para HLA-DRB (PCR-SSP) ou amplificaçäo gênica seguida de hibridaçäo com oligonucleotídeos específicos (PCR-SSOP) para HLA-DQA e DQB. Foram calculadas as freqüências gênicas e as freqüências haplotípicas DRB-DQB e DQA-DQB e a populaçäo mostrou estar em equilíbrio genético de acordo com a lei de Hardy-Weinberg. Finalmente, comparamos também os dados obtidos com os da populaçäo de Porto Velho, Rondônia, salientando a importância da obtençäo de dados regionais para os controles quando se estuda este complexo sistema genético.

Absence of linkage between MHC and a gene involved in susceptibility to human schistosomiasis

Six hundred million people are at risk of infection by Schistosoma mansoni, MHC haplotypes have been reported to segregate with susceptibility to schistosomiasis in murine models. In humans, a major gene related to susceptibility/resistance to infection by S. mansoni (SM1) and displaying the mean fecal egg count as phenotype was detected by segregation analysis. This gene displayed a codominant mode of inheritance with an estimated frequency of 0.20-0.25 for the deleterious allele and accounted for more than 50 percent of the variance of infection levels. To determine if the SM1 gene segregates with the human MHC chromosomal region, we performed a linkage study by the lod score method. We typed for HLA-A, B, C, DR and DQ antigens in 11 informative families from an endemic area for schistosomiasis in Bahia, Brazil, by the microlymphocytotoxicity technique. HLA-DR typing by the polymerase chain reaction with sequence-specific primers (PCR-SSP) and HLA-DQ were confirmed by PCR-sequence-specific oligonucleotide probes (PCR-SSOP). The lod scores for the different theta values obtained clearly indicate that there is no physical linkage between HLA and SM1 genes. Thus, susceptibility or resistance to schistosomiasis, as defined by mean fecal egg count, is not primarily dependent on the host's HLA profile. However, if the HLA molecule plays an important role in specific immune responses to S. mansoni, this may involve the development of the different clinical aspects of the disease such as granuloma formation and development of hepatosplenomegaly.