Peptidoglycan recognition proteins: modulators of the microbiome and inflammation.

All animals, including humans, live in symbiotic association with microorganisms. The immune system accommodates host colonization by the microbiota, maintains microbiota-host homeostasis and defends against pathogens. This Review analyses how one family of antibacterial pattern recognition molecules - the peptidoglycan recognition proteins - has evolved a fascinating variety of mechanisms to control host interactions with mutualistic, commensal and parasitic microorganisms to benefit both invertebrate and vertebrate hosts.