Immune sensing by activating and inhibitory C-type lectin receptors

Abstract

The innate immune system uses a defined set of germ-line-encoded pattern recognition receptors (PRRs) to recognize microbes or non-microbial forms of danger and subsequently activates an inflammatory response. In the last decade, several myeloid PRRs have been identified that utilize intracellular signaling modules called immunoreceptor tyrosine-based activation motifs (ITAMs). These ITAM-coupled C-type lectin domain-containing receptors (CLRs) recognize both pathogen-associated pattern (PAMPs) and host-derived danger molecules. To balance immunity, these CLRs can be counteracted by inhibitory receptors harboring an immunoreceptor tyrosine-based inhibitory motif (ITIM). This mini-review summarizes the current knowledge of the function and regulation of ITAM-and ITIM-coupled CLRs and their relevance in immune homeostasis and host defense.