CD300LF (CD300 molecule-like family member f), also known as NKIR (NK inhibitory receptor), IREM1 (immune receptor expressed on myeloid cells 1), CLM1 (CMRF35-like molecule 1) or IgSF13 (immunoglobulin superfamily member 13), is a 290 amino acid single-pass type I membrane protein that functions as an inhibitory receptor for myeloid cells and mast cells. As a member of the CD300 family, CD300LF contains one Ig-like V-type (immunoglobulinlike) domain and recruits SHP or SHIP to mediate negative regulatory signals. CD300LF inhibits osteoclast formation and is highly expressed in lung, spleen, peripheral blood leukocytes and monocytes.