Differential association of tumour necrosis factor-alpha single nucleotide polymorphism (-308) with tuberculosis and bronchial asthma.

Background. Tumour necrosis factor (TNF)-alpha is a pleiotropic, pro-inflammatory cytokine of 17 kDa, whose gene is localized on the short arm of chromosome 6. It has a G-308A polymorphism in the promoter region, which is known to be associated with its differential production; the A allele being the high producer. The circulating level of TNF-alpha is under genetic control and implicated in the pathophysiology of asthma and tuberculosis. Since raised levels of TNF-a have been found in asthma and tuberculosis, we looked for the association of TNF-alpha G-308A polymorphism in patients with these diseases. Methods. A total of 300 blood samples from patients (155 with asthma, 145 tuberculosis) and 211 normal healthy controls were collected. The G-308A polymorphism was studied using amplification refractory mutation system analysis. Results. The distribution of G/A alleles in the two patient groups when compared with normal controls revealed a statistically significant association with asthma (p = 0.016) but not with tuberculosis (p = 0.178). Conclusion. The data support the common variant common disease hypothesis, which emphasizes that common genetic variations may participate as critical players in inciting common diseases.