MAPK3 and bacterial infectious disease: To pinpoint how ERK1/2, JNK, and P38 are involved in CPS- or M. ovipneumoniae-induced apoptosis in ALI cultures of sheep bronchial epithelial cells, we further investigated impacts of U0126 (an ERK1/2 inhibitor), SP600125 (a JNK inhibitor), and SB203580 (a P38 inhibitor) on MAPK signaling in sheep bronchial epithelial cells in response to CPS stimulation or bacterial infection.