[Innate immunity and tuberculosis]

The immune system is divided into innate and adaptive immunity. The innate immune system provides the first line of host defense against invading microorganisms before the development of adaptive immune responses. Innate immune responses are initiated by germline-encoded pattern recognition receptors (PRRs), which recognize specific structures of microorganisms. Toll-like receptors (TLRs) are one of the family of pattern-recognition receptors to sense a wide range of microorganisms, such as bacteria, fungi, protozoa and viruses. Recognition of Mycobacterium tuberculosis components by TLRs triggers activation of signal transduction pathways, which then induces dendritic cell maturation and cytokine production, resulting in development of adaptive immunity. TLRs are critically involved in the induction of host defense to M. tuberculosis.