Recombinant Human KIR2DL5/CD158f Fc Chimera Protein, CF

KIR2DL5 (2DL5, designated CD158f) is a 60 kDa type I transmembrane glycoprotein that belongs to the killer cell Ig-like receptor (KIR) family (1, 2). KIRs are expressed on CD56^dim NK cells and T cell subsets where they regulate effector functions in the innate immune system (1 - 3). KIRs are named for the number of Ig-like domains (2D or 3D) in the extracellular domain (ECD), and whether they have long or short (L, S) cytoplasmic tails (3). Like other inhibiting KIRs, KIR2DL5 has two ITIM domains within its long tail; however, one of these is atypical and may cause KIR2DL5 to be less inhibitory than most inhibiting KIRs (4). Gene duplication is thought to have resulted in individual genes coding for KIR2DL5 A and B proteins that vary by only 2 amino acids (5). Individuals may express either KIR2DL5A or KIR2DL5B, both proteins, or neither protein (5). Within the KIR family, KIR2DL5 and KIR2DL4 form a subfamily. The two share 79% amino acid sequence identity, have longer cytoplasmic tails than other KIR, and each has one D0 and one D2-type Ig-like domain (1). However, KIR2DL5 is only inhibitory, while KIR2DL4 has characteristics of both activating and inhibiting KIR.