Tumour necrosis factor family genes in a phenotype of COPD associated with emphysema.

Genetic factors are believed to play a role in the individual susceptibility to chronic obstructive pulmonary disease (COPD). Tumour necrosis factor (TNF) family genes have been widely investigated but inconsistent results may lie either in the genetic heterogeneity of populations or in the poor phenotype definition. A genetic study was performed using a narrower phenotype of COPD. The authors studied 86 healthy smokers and 63 COPD subjects who were enrolled based on irreversible airflow obstruction (forced expiratory volume in one second/forced vital capacity <70\% predicted) and a diffusing capacity for carbon monoxide <50\% predicted (moderate-to-severe COPD associated with pulmonary emphysema). The following polymorphisms were investigated: TNF-308, the biallelic polymorphism located in the first intron of the lymphotoxin-alpha gene, and exon 1 and exon 6 of the TNF receptor 1 and 2 genes, respectively. No significant deviations were found concerning the four polymorphisms studied between the two populations. The authors confirm that the tumour necrosis factor family genes, at least for the polymorphisms investigated, are not major genetic risk factors for chronic obstructive pulmonary disease in Caucasians, either defined in terms of emphysema (this study) or airflow obstruction (previous studies). Nevertheless, the authors would like to emphasise the importance of narrowing the phenotype in the search for genetic risk factors in chronic obstructive pulmonary disease.