Human Killer Cell Immunoglobulin-Like Receptor 2DL4 (KIR2DL4) Protein

Background

KIR2DL4 is a member of the killer cell immunoglobulin-like receptor (KIR) family, which plays an essential role in immune regulation, particularly through the modulation of natural killer (NK) cell activity. KIR2DL4 is unique among KIRs in its ability to transduce both activating and inhibitory signals, allowing it to play a nuanced role in immune responses. Unlike most KIRs, which are specific to either HLA-A, -B, or -C, KIR2DL4 binds specifically to HLA-G, a non-classical MHC class I molecule. HLA-G is primarily expressed in tissues with immune privilege, such as the placenta, where it contributes to immune tolerance, thus implicating KIR2DL4 in maternal-fetal immune interactions. The gene encoding KIR2DL4 is located on chromosome 19q13.4, within the leukocyte receptor complex (LRC), alongside other KIR genes. The KIR family is highly polymorphic, resulting in a wide array of receptor-ligand combinations that contribute to individual variations in immune responses. KIR2DL4’s interaction with HLA-G is particularly important for its role in promoting tolerance in pregnancy and its potential involvement in immune responses to certain infections and cancers.