Analysis of IL-4 promoter and VNTR polymorphisms in Thai patients with pulmonary tuberculosis

Tuberculosis (TB) is a leading cause of morbidity and mortality in Thailand. Cytokines play important roles in defense against Mycobacterium tuberculosis infection. Interleukin (IL)-4 is one of the anti-inflammatory cytokines and has been found to be elevated in TB patients. The common polymorphisms in IL-4 gene, including IL-4-590C/T, IL-4-33C/T, and IL-4-variable number of tandem repeats (VNTR) intron 3 have been reported to be associated with risk for some diseases. The purpose of this study was to investigate possible associations between the above mentioned three common functional polymorphisms in the IL-4 gene in patients with pulmonary tuberculosis (PTB) in a Thai population. Forty three patients with PTB and 90 healthy control subjects were studied. The three common polymorphisms of the IL-4 gene were determined using polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP). The allele and genotype frequencies of IL-4 -590 C/T, -33 C/T, VNTR intron 3 polymorphisms did not show significant differences between PTB patients and healthy controls (genotype: p=0.88, p=0.92, p=0.40; allele: p=0.38, p=0.44, p=0.53, respectively). However, the allele distribution of the IL-4 -590 C, -33 C, and VNTR R3 was higher among PTB patients (25.58%, 25.58%, 25.58%, respectively) than among control subjects (20%, 20.48%, 19.44%, respectively). This may suggest that IL-4-590C/T, -33C/T and VNTR intron 3 might play a role in susceptibility to PTB. A larger cohort may possibly help conclude our findings.