TLR-independent pattern recognition receptors and anti-inflammatory mechanisms

Pattern recognition receptors recognize molecular patterns associated with the surfaces of microbes and apoptotic cells. These receptors act alone and in concert to bind, phagocytose, and transduce cellular signals derived from these molecular patterns. The outcome of these interactions is dependent on the nature of the ligands, and upon the nature and combination of the ligated receptors. Whereas much attention has been focused on the properties and activities of the Toll-like receptors (TLRs) in this process, many other pattern recognition molecules have been described. Here we review some of these non-TLR receptors and their ligands, and focus attention on the mannose binding lectin, a humoral pattern recognition molecule. In addition, we describe how recognition of apopotic cells via pattern recognition receptors appears to result in responses that differ from those elicited by microbial ligands.