Generating a T cell tumor-specific immune response in vivo: can flt3-ligand-generated dendritic cells tip the balance?

flt3 ligand (FL) is a growth factor that induces hematopoietic progenitor c ell and dendritic cell (DC) expansion when administered to mice. Lymphoid-r elated (CD8 alpha(+)) and myeloid-related (CD8 alpha(-)) DC are transiently expanded in multiple tissues. Treatment of tumor-bearing mice with FL resu lts in slower tumor growth and, in some cases, tumor rejection and the deve lopment of tumor-specific T cell immunity. The clinical use of DC as cellul ar vehicles for tumor antigen presentation to generate a tumor-specific T c ell response is under investigation. DC are currently generated ex vivo, pu lsed with antigen, and then infused into patients, and much effort is being directed toward optimizing each of these steps. Administration of FL to hu mans induces a profound increase in circulating DC. The availability of a l arge number of DC generated in vivo has important implications for tumor im munotherapy approaches.