Immuno‐genetic importance of Th17 in susceptibility to TB

Tuberculosis is a highly infectious disease caused by Mycobacterium tuberculosis (M. tb) which is infecting around one‐third of the world population. The majority of individuals develop latent tuberculosis infection (LTBI), but only 10% of LTBI individuals develop active TB. Household contacts (HHC) of TB patients are 10‐60 times more likely to develop the disease than non exposed individuals. Dendritic cells strengthen the immune response against M. tb through the stimulation of CD4+T cells, which differentiate into different types of T helper cells (Th) such as Th1, Th2 and Th17 lineages. Th17 cells play an important role in coordinating pulmonary immune defence and enhance the expression of cytokines (IL‐17A, IL‐17F, IL‐21 and IL‐22), chemokines and antimicrobial peptides that lead to phagocytosis of M. tb. Previous studies have reported that Th17 polymorphisms are associated with TB susceptibility. In this review, we focused on the immuno‐genetic importance of Th17 in TB and screening the HHC for Th17 genetic variants may help for the early detection of TB infection in individuals who are at risk.