Plants also have receptors that can cause a response to chitin, namely chitin elicitor receptor kinase 1 and chitin elicitor-binding protein.  The first chitin receptor was cloned in 2006.  When the receptors are activated by chitin, genes related to plant defense are expressed, and jasmonate hormones are activated, which in turn activate systemic defenses.  Commensal fungi have ways to interact with the host immune response that, , were not well understood.
Some pathogens produce chitin-binding proteins that mask the chitin they shed from these receptors. Zymoseptoria tritici is an example of a fungal pathogen that has such blocking proteins; it is a major pest in wheat crops.