Abstract: Objective To investigate the role of TRAF2 on AP-1 signaling pathway in human B cells. Methods Human Ramos B cells were transfected with plasmids expressing YFP fusion wild type TRAF2 (YFP-WT-TRAF2) or YFP fusion dominant-negative TRAF2 (DN-TRAF2), or transfected with shRNA-TRAF2 and control shRNA plasmid. After cultured overnight, cells were either sorted with flowcytometry or screened by antibiotics G418. Activation of AP-1 pathway, including phosphorylation of ERK, JNK and P38, as well as nuclear translocation of AP-1 subunits were detected by western blot and ELISA. Results Overexpression of WT-TRAF2 selectively induced activition of MAPK by phosphorylation of ERK and P38,and further induced nuclear translocation of c-fos. Moreover, both overexpression of DN-TRAF2 and shRNA-TRAF2 transfected cells inhibited phosphorylation of ERK and P38,and nuclear translocation of c-fos. Conclusion TRAF2 selectively activates some kinases in CD40 mediated AP-1 signaling pathway, and plays an important role in AP-1 activation.