Target Pattern Recognition in Innate Immunity

Target pattern recognition in innate immunity is responsible for the immediate, usually protective, responses shown against invading microorganisms, and it is the principal feature of self and non-self recognition by virtue of the recognition of structures on the microbial pathogens, which are not found on host cells. This is an area that has been very actively researched, over approximately the past 12 years, and therefore this volume provides a timely comprehensive, and up to date, summary of the types and range of cell surface, intracellular, and secreted, host proteins involved in the recognition of microbial products, and of the protective mechanisms triggered as a result of the recognition events.

The Toll-like receptors, first described in Drosophila and now well-characterised on human cells, provide an excellent demonstration of the wide range of different microbial products recognised by this family of receptors and of the signalling pathways which are triggered thus leading to induction of inflammatory cytokines and the activation of genes producing antimicrobial products. In addition, several cell surface proteins involved in target pattern recognition have been described on the surfaces of macrophages (macrophage mannose receptor and macrophage scavenger receptors), and on dendritic cells (DEC205), and to be involved with the uptake and clearance of whole microorganisms and polyanioic ligands. Pattern recognition is also utilised by intracellular receptors, with NOD-like receptors in the cytosol recognizing microbial molecules and activating the production of inflammatory cytokines or pathways that induce the production of inflammatory molecules. Secreted proteins, such as the pentraxins, which includes the acute phase reacting, C-reactive protein (CRP) and serum amyloid protein (SAP), and the collectins (mannan binding lectin, lung surfactant protein A and D) and ficolins can also readily recruit killing and clearance systems. Indeed, the serum