CD40 and systemic lupus erythematosus: Interestingly, a simultaneous ligation of α5β1 and CD40 was shown to result in a synergistic effect involving the activation of ERK1/2 and p38 signaling pathways as well as the production of MMP-2 and -9 [70], responses usually exhibited in arthritic inflammatory conditions such as SLE and RA [72,73].