IRF4 deletion led to impaired BMDM migration in vitro. BMDMs were isolated from IRF4f/f (WT) and LysM-Cre IRF4f/f (MΦ IRF4−/−) mice, and were immediately used for in vitro Transwell migration assays. (A) Chemotactic responses to 10% FBS, fMLP, and CX3CL1 were markedly lower for IRF4−/− BMDMs than WT BMDMs. ***P<0.001, n=4–6. (B) Chemotactic responses to CCL19 and CCL21 were also significantly lower for IRF4−/− BMDMs than WT BMDMs. ***P<0.001, n=5.