Immune Response to Mycobacteria

The immune response to mycobacteria is a complex process, varying according to the infection or disease involved and to its acute or chronic nature; it is not yet fully understood. A better understanding is essential for definitive diagnosis and the development of new vaccines. The immune response involves a wide range of molecular and Th1- model cellular components: antigen-presenting cells (macrophages and dendritic cells); T lymphocytes (CD4, CD8, NK and γδ); cytokines such as IL-2, IFN-γ, IL-18 and TNF-α; and the chemokines RANTES, MCP-1, MIP-1α and IL-8, which play a key role in granuloma formation in M. tuberculosis and atypical mycobacterial infection. The immune response also involves epithelial and natural killer (NK) cells, several signaling proteins (costimulatory molecules and transcription factors) that participate in regulating T-cell activation, toll-like receptors and major histocompatibility complex Class 1 molecules. M. tuberculosis-secreted antigens that reportedly induce the secretion of mediators associated with protection against M. tuberculosis infection include CPF-10, ESAT-6, 27kDa and 38 kDa, which induce production of IFN-γ, TNF-α and nitric oxide. The immune response to M. leprae infection involves the Th-1 model in tuberculoid leprosy and the Th-2 model in lepromatous leprosy, with the production of IL-4, IL-5 and IL-13 or IL-10 (Th-3 response).