CD300a is an inhibitory receptor in the Ig superfamily, a type I transmembrane protein containing immunoreceptor tyrosine-based inhibitory motifs (ITIMs) on its cytoplasmic tail. Human CD300a (CMRF-35H, IRp60) and mouse CD300a (CLM-8, LMIR-1, MAIR-I) are functional orthologs, expressed by monocytes, granulocytes, mast cells, and subsets of B cells. Human, but not mouse, CD300a is also expressed by unstimulated NK cells and subsets of T cells. Phosphorylated ITIMs are able to recruit different phosphatases, such as SHP-1 and SHP-2, leading to inhibition of cell activation.
