Dendritic Cell Immunoreceptor (DCIR): An ITIM-Harboring C-Type Lectin Receptor
C-type lectin receptors (CLRs) have been recognized as one of the pattern recognition receptors that trigger immune responses against pathogens. Dendritic cell immunoreceptor (DCIR) is a type II membrane protein that contains an extracellular carbohydrate recognition domain (CRD) and a long cytoplasmic tail with an immunoreceptor tyrosine-based inhibition motif (ITIM). Only one molecular species is identified in humans (DCIR), while four family molecules (DCIR1-4) are present in mice. Human DCIR and mouse DCIR1 dampen immune responses through ITIM-mediated reaction. DCIR binds mannose and fucose and also pathogenic organisms, but the structure of the ligand carbohydrates still remains to be determined. DCIR1 is important for the homeostasis of the immune system, and the deficiency causes autoimmune diseases. DCIR also acts as an attachment factor for HIV in dendritic cells and HIV-infected T cells. DCIR1 is also implicated in the pathogenesis of mosquito-transmitted virus and protozoan infections. This chapter highlights the roles of human and mouse DCIR in immune responses and immune homeostasis revealed by in vitro cell-based studies as well as in vivo gene-depleted mouse analyses.
KeywordsC-type lectins HIV Phosphatases ITIM Homeostasis Bone metabolism
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