Early dynamics of innate immunity during pulmonary tuberculosis.

Tuberculosis (TB) most frequently affects the lung, with Mycobacterium tuberculosis (Mtb), the etiologic agent of TB, promptly gaining access to lung-resident myeloid cells, notably alveolar macrophages. Historical observational case-contact surveys and recent epidemiological studies report on resistors. These individuals are likely protected against infection by defence mechanisms occurring promptly after bacterial exposure. The early events proceeding within the Mtb-infected lung are critical for the outcome of the infection. Despite the heightened relevance of the first contact between Mtb and the host, the current understanding of precise immune events occurring shortly after Mtb exposure is still limited. More recently, new information has emerged and we here summarize cellular and molecular events of innate immunity, considering the lung compartments and cellular communication over time. We discuss new concepts emerging from experimental models of pulmonary TB, highlight recent advances and summarize requirements for accurate mapping of early events in TB. A better understanding of disease pathogenesis at incipient stages will facilitate the development of novel therapeutics and more effective prophylactic measures for TB.