The balance between protective and pathogenic immune responses in the TB-infected lung.

Tuberculosis is a disease of the lung, and efficient transmission is dependent on the generation of a lesion in the lung, which results in a bacterium-laden cough. Mycobacterium tuberculosis (Mtb) is able to manipulate both the innate and acquired immune response of the host. This manipulation results in an effective CD4(+) T cell response that limits disease throughout the body but can also promote the development of progressively destructive lesions in the lung. In this way Mtb infection can result in an ambulatory individual who has a lesion in the lung capable of transmitting Mtb. The inflammatory environment within the lung lesion is manipulated by Mtb throughout infection and can limit the expression of acquired immunity by a variety of pathways.