The killer-cell immunoglobulin-like receptors of macaques

Natural killer (NK) cells play a central role in immune responses through direct cytotoxicity and the release of cytokines that prime adaptive immunity. In simian primates, NK cell responses are regulated by interactions between two highly polymorphic sets of molecules: the killer-cell immunoglobulin-like receptors (KIRs) and their major histocompatibility complex (MHC) class I ligands. KIR-MHC class I interactions in humans have been implicated in the outcome of a number viral diseases and cancers. However, studies to address the role of KIRs in animal models have been limited by the complex immunogenetics and lack of defined ligands for KIRs in non-human primates. Due to the rapid evolution of KIRs, there is little conservation among the KIR genes of different primate species and it is not possible to predict the specificity of KIRs from known KIR-MHC class I interactions in humans. Hence, the MHC class I ligands for KIRs in species other than humans are poorly defined. Here, we review the KIR genes of the rhesus macaque, an important animal model for human immunodeficiency virus infection and other infectious diseases, and the MHC class I ligands that have been identified for KIRs in this species.