Promoter polymorphism of IL-8 gene and IL-8 production in pulmonary tuberculosis

Interleukin-8 (IL-8) is a chemokine which functions as a potent chemo attractant for the recruitment of leucocytes to the inflammatory sites. A polymorphism in position –251 in the promoter region of the IL-8 gene has been shown to be associated with altered IL-8 production. IL-8-251A promoter polymorphism was studied in 127 pulmonary tuberculosis (PTB) patients and 124 normal healthy subjects (NHS). IL-8 gene variants were correlated with IL-8 levels from peripheral blood mononuclear cells stimulated with phytohaemagglutinin, culture filtrate antigen (CFA) of Mycobacterium tuberculosis and live M. tuberculosis. No difference was observed in the variant genotype frequencies of IL-8 gene and IL-8 levels between NHS and PTB patients. NHS positive for TT genotype showed a higher spontaneous IL-8 production than AA genotype (P = 0.05). Similarly, PTB patients with TT genotype showed significantly higher IL-8 production to CFA (P = 0.009) and live M. tuberculosis (P = 0.022), compared to patients with AA genotype. The study suggests that the variant genotypes of –251 promoter polymorphism of the IL-8 gene are not associated with susceptibility to PTB. Probably, TT genotype may be associated with higher IL-8 production and increased leucocyte accumulation and inflammation at the site of M. tuberculosis infection.