Any series of molecular signals generated as a consequence of a pattern recognition receptor (PRR) binding to one of its physiological ligands. PRRs bind pathogen-associated molecular pattern (PAMPs), structures conserved among microbial species, or damage-associated molecular pattern (DAMPs), endogenous molecules released from damaged cells. [ https://www.worldcat.org/search?q=bn%3A0781735149 http://www.ncbi.nlm.nih.gov/pubmed/15199967 ]