Recognition of Mycobacteria by Dendritic Cell Immunoactivating Receptor

Mycobacteria have unique lipids on their cell walls, and the structures and physiological activities of these lipid components have been the subject of many studies. Although the host receptors for mycobacterial lipid have long been elusive, in recent years C-type lectin receptors (CLRs) have been reported to recognize these components. The dendritic cell immunoactivating receptor (DCAR), a CLR member, is encoded by Clec4b1. DCAR, which was identified in 2003, is reported to be associated with the immunoreceptor tyrosine-based activation motif (ITAM)-containing adaptor protein, the Fc receptor γ chain (FcRγ). However, its physiological ligand and biological function were unknown. We recently identified DCAR as an activating receptor for mycobacteria. DCAR recognizes acylated phosphatidyl-inositol mannosides (PIMs) in mycobacteria to promote Th1 responses during mycobacterial infection. This review summarizes recent discoveries about the ligands and immunological roles of DCAR.