1. Phagocytosis and immune recognition of M. tuberculosis.
Phagocytosis and immune recognition of M. tuberculosis. Various receptors have been identified for phagocyosis of M. tuberculosis (MTB) by macrophages and dendritic cells: complement receptors are primarily responsible for uptake of opsonized M. tuberculosis; MRs and scavenger receptors for uptake of nonopsonized M. tuberculosis. TLRs play a central role in immune recognition of M. tuberculosis. In the context of CD14, TLR2 binds lipoarabinomannan, a heterodimer of TLR2 and TLR6 binds a 19-kDa M. tuberculosis lipoprotein, TLR4 binds to an undefined heat-labile cell-associated factor, and (possibly) TLR9 binds to M. tuberculosis DNA. After binding to TLRs, common signalling pathways lead to cell activation and cytokine production. TLRs are expressed not only at the cell surface but also in phagosomes; therefore, immune activation may occur with or without phagocytosis. On the other hand, phagocytosis alone probably does not lead to immune activation without the involvement of TLRs.
Reinout van Crevel et al. Clin. Microbiol. Rev. 2002; doi: /CMR