Monocyte CD40 expression in head and neck squamous cell carcinoma (HNSCC).

CD40, an antigen-presenting cell expressed costimulatory receptor molecule, binds to T cell expressed CD40-ligand (CD40-L). Using a mouse tumor model, we showed previously that lower CD40/CD40-L expression levels promoted tumor growth whereas higher CD40/CD40-L expression levels led to tumor regression indicating duality in CD40 functions. Whether CD40/CD40-L expressions are regulated in cancer patients is unknown.