A PEPTIDOGLYCAN RECOGNITION PROTEIN IN INNATE IMMUNITY CONSERVED FROMINSECTS TO HUMANS

Innate nonself recognition must rely on common structures of invading microbes. In a differential display screen for up-regulated immune gen es in the moth Trichopulsia ni we have found mechanisms for recognitio n of bacterial cell wall fragments. One bacteria-induced gene encodes a protein that, after expression in the baculovirus system, was shown to be a peptidoglycan recognition protein (PGRP). It binds strongly to Gram-positive bacteria. We have also cloned the corresponding cDNA fr om mouse and human and shown this gene to be expressed in a variety of organs, notably organs of the immune system-i.e., bone marrow and spl een. In addition, purified recombinant murine PGRP was shown to posses s peptidoglycan affinity. From our results and the sequence homology, we conclude that PGRP is a ubiquitous protein involved in innate immun ity, conserved from insects to humans.