CSF3 and infection: Since p38α MAPK is the major isoform, we then investigated whether it was involved in the SB203580-induced enhancement of the LPS-induced increase in the G-CSF mRNA levels using p38α MAPK knockdown in RAW264.7 cells by infection with a lentivirus carrying a specific shRNA targeting p38α MAPK or a lentivirus carrying luciferase shRNA as a negative control.