Killer Cell Immunoglobuline-like Receptors (KIR)
Dr. med. Kaimo Hirv
KIRs are expressed on natural killer (NK) cells. They bind specific HLA molecules and have the task to recognize cells with lacking or down-regulated HLA expression. Cells infected with a virus or tumor cells that are able to suppress HLA expression can be identified via KIRs and eliminated by NK cells. So far, 16 KIR genes have been characterized that are likewise polymorphic as HLA genes but are located outside of the MHC locus on chromosome 19 (19q13.4) in the KIR locus.
The role of KIR regarding blood stem cell transplantation has not been completely clarified yet. There is indication, however, that the compatibility of KIR ligands (HLA molecules) or even certain KIR genes themselves correlate with GVHD and the frequency of recurrences after transplantations. Moreover, there seems to be an association between certain KIR allele states with preeclampsia and habitual abortions. In women with habitual abortions certain genes for several activating KIRs could not be detected. Furthermore an association between certain KIR genotypes and infectious and autoimmune diseases was described.