Self-referent MHC type matching in frog tadpoles

Self/non-self recognition mechanisms underlie the development, immunology and social behaviour of virtually all living organisms, from bacteria to humans. Indeed, recognition processes lie at the core of how social cooperation evolved. Much evidence suggests that the major histocompatibility complex (MHC) both facilitates nepotistic interactions and promotes inbreeding avoidance. Social discrimination based on MHC differences has been demonstrated in many vertebrates but whether the labels used in discrimination are directly associated with the MHC, rather than with other genes with which it covaries, has remained problematic. Furthermore, effects of familiarity on natural preferences have not been controlled in most previous studies. Here we show that African clawed frog (Xenopus laevis) tadpoles discriminate among familiar full siblings based on MHC haplotype differences. Subjects (N=261) from four parental crosses preferred siblings with which they shared MHC haplotypes to those with no MHC haplotypes in common. Using only full siblings in experimental tests, we controlled for genetic variation elsewhere in the genome that might influence schooling preferences. As test subjects were equally familiar with stimulus groups, we conclude that tadpole discrimination involves a self-referent genetic recognition mechanism whereby individuals compare their own MHC type with those of conspecifics

Speed and selection in the evolution of killer-cell immunoglobulin-like receptors

The killer-cell immunoglobulin-like receptors (KIR) form a diverse family of receptors that control the functions of natural killer cells. Sequencing of KIR from primates has revealed the unexpected extent to which this gene family has diversified mostly likely in response to pathogens and to pathogen-mediated selection of their MHC class I ligands. Human KIR diversity is now a burgeoning area for disease association studies. This review examines the evolution of KIR from a primate-centric view in order to rationalize our current knowledge of the diversity of human KIR