Killer Cell Immunoglobulin-like Receptor

The killer cell immunoglobulin - like receptors ( KIR short or KIR receptors) are receptors that occur mainly in the plasma membrane of natural killer cells ( NK cells), that constitute a part of the immune system of mammals. With the aid of the KIR - NK cell recognizes abnormal cells, such as tumor cells or infected cells of microorganisms. This is done with the help of short peptides that each cell takes its metabolism and presented at the plasma membrane (see Major Histocompatibility Complex ). At this KIR can now bind or not and so distinguish between diseased and healthy cells.

The KIR genes form a gene family located on human chromosome 19 ( locus 19q13.4 ) and belongs to the immunoglobulin superfamily. The proteins encoded by these genes receptors are expressed almost exclusively on NK cells; However, there are a small subpopulation of T cells that also express KIR on the cell surface. The KIR in humans and other primates, the most important NK cell receptors, while the Ly49 molecules take similar function in mice.

A distinction is made between the KIR activating and inhibitory receptors, which differ mainly in the transmembrane region and the cytoplasmic tail. Both the inhibitory and the activating serve MHC class I molecules as ligands.

In humans there are 14 KIR genes, but the number of available KIR genes varied in the genome of different people. The expression of different combinations of KIR molecules varies in the cells, wherein each expression patterns of the receptors is transmitted to the daughter cells by methylation of the non- expressed KIR genes.