Beside adaptive specific immunity, an innate immunity plays a significant role in GALT because it provides more rapid response. Recognition of microbial non-self signature occurs by pattern recognition receptors (PRR) that can be found on dendritic cells, macrophages, monocytes, neutrophils and epithelial cells. PRRs bind to conserved microbial pattern like cell walls components (LPS, teichoic acid, flagellin, peptidoglycan) or viral or bacterial nucleic acid. PRRs are localized extracellularly as membrane-bound receptors (Toll-like receptors) or intracellularly (NOD-like and RIG-like receptors). Varied palette of pattern recognition receptors is activated by various signals named PAMP (pathogen associated molecular patterns) or by signals connected to tissue damage named DAMP (damage associated molecular patterns).