RESUMO
Recent evidence suggests that deficiency in the Th1 cytokine pathway may underlie the susceptibility to allergic asthma. This study examined whether (1) single-nucleotide polymorphisms exist in the promoter region of the two interleukin (IL)-12 subunit genes in patients with asthma; (2) messenger RNA and protein expressions of signal transducers and activators of transcription, IL-12, IFN-gamma, and their receptors are altered in asthma; and (3) linkage to genes in the Th1 pathway is present in families with asthma in Iceland. The promoter regions of the IL-12 subunit genes were sequenced in 94 patients with asthma and 94 control subjects without asthma. Linkage was examined in 169 families that included over 570 patients with asthma and 950 of their unaffected relatives. The results demonstrate no evidence of linkage to microsatellite markers in close association with genes within the Th1 pathway, and no polymorphism was detected in the promoter regions of the two IL-12 subunit genes in the cohort with asthma patients. Moreover, we found no differences in the messenger RNA or protein expression signals of genes in the IL-12 pathway between the patients and control subjects. We conclude that decrease in Th1 type cytokine response is unlikely to present a primary event in asthma.
Assuntos
Asma/genética , Hipersensibilidade Imediata/genética , Interferon gama/genética , Interleucina-12/genética , Células Th1 , Adolescente , Adulto , Asma/epidemiologia , Asma/imunologia , Estudos de Casos e Controles , Criança , Ensaio de Imunoadsorção Enzimática , Feminino , Citometria de Fluxo , Ligação Genética/genética , Ligação Genética/imunologia , Genótipo , Humanos , Hipersensibilidade Imediata/epidemiologia , Hipersensibilidade Imediata/imunologia , Interferon gama/imunologia , Interleucina-12/imunologia , Masculino , Repetições de Microssatélites/genética , Repetições de Microssatélites/imunologia , Pessoa de Meia-Idade , Fenótipo , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único/genética , Regiões Promotoras Genéticas/genética , Regiões Promotoras Genéticas/imunologia , RNA Mensageiro/genética , RNA Mensageiro/imunologia , Transdução de Sinais/genética , Transdução de Sinais/imunologia , Células Th1/imunologia , Transcrição Gênica/genética , Transcrição Gênica/imunologiaRESUMO
Asthma is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Numerous loci and candidate genes have been reported to show linkage and association to asthma and atopy. Although some studies reporting these observations are compelling, no gene has been mapped that confers a sufficiently high risk of asthma to meet the stringent criteria for genomewide significance. Using 175 extended Icelandic families that included 596 patients with asthma, we performed a genomewide scan with 976 microsatellite markers. The families were identified by cross-matching a list of patients with asthma from the Department of Allergy/Pulmonary Medicine of the National University Hospital of Iceland with a genealogy database of the entire Icelandic nation. We detected linkage of asthma to chromosome 14q24, with an allele-sharing LOD score of 2.66. After we increased the marker density within the locus to an average of one microsatellite every 0.2 cM, the LOD score rose to 4.00. We designate this locus "asthma locus one" (AS1). Taken together, these results provide evidence of a novel susceptibility gene for asthma on chromosome 14q24.
