MAPK1 and infection: In response to pathogen infection, the activation of pattern recognition receptors (PRRs) [7], including the Toll-like receptors (TLRs), on the host’s cells surface activates multiple downstream signaling pathways, including the members of each of the major mitogen-activated protein kinase (MAPK) subfamilies—the extracellular signal-regulated kinase (ERK), p38, and Jun N-terminal kinase (JNK) subfamilies.