Genetic and functional diversity of allorecognition receptors in the urochordate, .

Allorecognition in is controlled by a highly polymorphic locus (the ), and functionally similar to missing-self recognition utilized by Natural Killer cells-compatibility is determined by sharing a self-allele, and integration of activating and inhibitory signals determines outcome. We had found these signals were generated by two -encoded receptors, called and Here we show that genes are members of an extended family consisting of >37 loci, and co-expressed with an even more diverse gene family-the (). The are membrane proteins related to , but include conserved tyrosine motifs, including ITIMs and hemITAMs. Both genes are encoded in highly polymorphic haplotypes on multiple chromosomes, revealing an unparalleled level of diversity of innate receptors. Our results also suggest that ITAM/ITIM signal integration is a deeply conserved mechanism that has allowed convergent evolution of innate and adaptive cell-based recognition systems.