Recombinant Human CD300c Fc Chimera Protein, CF

Leukocyte mono-Ig-like receptor 2 (LMIR2; also CMRF-35, CMRF35-A antigen, and CD300c antigen) is a 23 kDa (predicted) type I transmembrane glycoprotein that belongs to the immunoregulatory signaling (IRS) family of molecules within the immunoglobulin (Ig) superfamily (1-4). Human LMIR2 is synthesized as a 224 amino acid (aa) precursor that has a 20 aa signal sequence, a 163 aa extracellular domain (ECD), a 21 aa transmembrane region, and a 20 aa cytoplasmic tail (SwissProt # Q08708). The ECD contains an Ig-like V-type domain (aa’s 22-128) and two N-linked glycosylation sites (aa’s 90 and 99). Downstream of the Ig V-domain, the membrane proximal region of LMIR2 (aa 128-183) contains a high proportion of proline (18%), serine (20%) and threonine (13%) residues (1). The transmembrane segment contains a charged glutamic acid that contributes to cell activation (1-3). Human LMIR2 shares 52% aa sequence identity with the mouse LMIR2, which is also known as CLM4. Human LMIR2 is 90% identical to human LMIR1 within the Ig-like domain. LMIR2 is present on the surface of natural killer cells, granulocytes, most myeloid cells, dendritic cells, and a subpopulation of T and B lymphocytes (1, 3). Mouse LMIR2 has the characteristics of an activatory molecule capable of inducing cellular activation and effector function in most cells and macrophages (3). The ligand for LMIR2 is presently unknown.