The series of molecular signals initiated by a ligand binding to a pattern recognition receptor (PRR), and ending with the regulation of a downstream cellular process, e.g. transcription. 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 GOC:ar http://www.ncbi.nlm.nih.gov/pubmed/15199967 GOC:add ]