Final answer:
Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens, triggering the engulfment and destruction of the pathogens by immune cells.
Step-by-step explanation:
Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs) on pathogens. These PAMPs are characteristic features expressed by viruses, bacteria, and parasites that differ from molecules on host cells. PRRs, such as Toll-like receptors (TLRs), are present on phagocytic cells like macrophages and dendritic cells, which detect and bind to PAMPs, triggering the engulfment and destruction of the pathogens.