FUNCTIONAL POLYMORPHISM OF THE PRO-INFLAMMATORY CYTOKINE GENES IN PULMONARY TUBERCULOSIS

In the present time, incidence of pulmonary tuberculosis (TB) becomes broader, due to spreading resistance of Mycobacterium tuberculosis (MBT) to anti-tuberculosis drugs and infection with highly virulent strains of M. tuberculosis. The MBT antigens can cause dysfunction of the receptors and modulate the cytokine secreting function of immunocompetent cells. Polymorphic genes of pro-inflammatory cytokines involved in the mechanisms of defense responses of innate immunity, determine the degree of resistance to individual mycobacterial infection, as well as severity and duration of the disease in cases of clinical manifestations. The aim of the study was to investigate the connections between allelic polymorphisms of IL2, IFNG and TNFA genes and changes in secretion of the corresponding pro-inflammatory cytokines IL-2, IFNγ, and TNFα in vitro in patients with the newly diagnosed pulmonary tuberculosis (TB), depending on the clinical form of the disease.

A total of 334 patients (220 men and 114 women) aged 23 to 50 years with newly diagnosed infiltrative and disseminated TB were enrolled into the study. The control group consisted of 183 healthy donors (130 men and 53 women) of corresponding age. The material of the research included DNA extracted from the whole blood and supernatants of culture suspensions of mononuclear leukocytes isolated from venous blood in healthy volunteers and patients with TB. The evaluation of cytokines secretion was performed by measuring their concentration in the blood mononuclear cell culture supernatants. using enzyme-linked immunosorbent assay (ELISA). To study polymorphic regions of cytokine genes, a polymerase chain reaction (PCR) was applied. Analysis of the obtained data was carried out by means of the program Statistica for Windows Version 6.0 (StatSoft Inc., USA).

It was found that the imbalance of secretion of pro-inflammatory cytokines in TB patients was associated with the polymorphic variants of genes of these cytokines. It was found that the hypo-secretion of IL-2 is determined by the carriage of the G allele and genotype GG (T-330G) of the IL2 gene in both the control group and in patients with TB, regardless of the clinical form. In patients with DTB carriers of the homozygous genotype TT (T-330G) of the IL2gene, increased protein secretion was established. The maximum secretion of TNFб was recorded in patients with the AA genotype (G-308A) of the TNFA gene in the control group and in ITB patients; the minimum concentration of TNFα was associated with the carrier of the homozygous GG genotype (G-308A) of the TNFA gene in all the examined groups. In patients with ITB and DTB, an increase in IFNγ secretion by mononuclear blood leukocytes is not associated with the carrier of polymorphism +874A/T of the IFNG gene.

Reduced secretion of IL-2 and TNFα in TB patients is associated with polymorphisms of their genes – (T-330G) of IL2 gene and (G-308A) of TNFA gene, respectively. The polymorphism (+874A/T) of the IFNG gene does not have a modulatory effect on the secretion of IFNγ in patients with TB, regardless of clinical form of the disease.

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