PAMPs-triggered immunity (PTI). Structural molecules specific to a class of microbes (PAMPs/MAMPs) are recognized by host pattern recognition receptors (PRRs), which trigger the immune response. PRRs can bind directly to microbes (e.g., PGRP-SA to Gram-positive bacteria) or more frequently sense microbes by sensing MAMPs released by microbes (indirect mode). PRRs can be secreted, transmembrane, phagosomal, or intracellular (not shown). They can initiate a transcriptional program or directly trigger effector modules.
