CD40 and infection: As a key co-stimulatory molecule in T cell, CD40 is critical for body's defense against invading pathogens, and plays essential role in adaptive immunity by eliciting survival, proliferation, differentiation and/or cell death signaling pathways (54, 55), and so, contributes much to immune response against pathogen infection (56), however, these immune responses often accompany inflammatory response (56–58).