MAPKs are activated in response to G-protein coupled receptors (GPCRs), growth factors, mitogens, pathogen associated molecular patterns (PAMPs) like LPS, inflammatory cytokines and environmental stresses. The kinase signalling cascade is organized into a three-tier system, with the activated MAP3Ks activating MAP2Ks, which in turn activate the MAPKs. There is significant crosstalk between the pathways and different MAPKs can activate different TH cell specific transcription factors, that signal the T cells to differentiate accordingly. ERKs and p38 family members are specific for TH2 and TH1 cells respectively. While the role of p38 in TH2 cells remains debated, JNKs are specific inhibitors of TH2 cells. The different pharmacological inhibitors of the MAPKs are also shown.
