Poly(D,L-lactide-co-glycolide) (PLGA) microspheres are biodegradable antigen delivery devices for loading of dendritic cells with antigen and toll-like receptor ligand in vitro and in vivo. They possess useful characteristics such as an adjustable drug release profile and a very high encapsulation efficiency. Dendritic cells efficiently take up the microspheres, process the microencapsulated antigens and present them on MHC class I and II molecules. Vaccination of mice with these two compound microspheres led to robust CTL responses strong enough to eliminate pre-established model tumors and to protect mice from vaccinia virus infection. Moreover, we could show that immunotherapy with microspheres charged with lysates of prostate carcinoma cells together with the toll-like receptor ligands CpG oligonucleotides and polyI:C interferes with the growth of prostate carcinoma in the preclinical transgenic adenocarcinoma mouse prostate (TRAMP) model, which closely resembles the human disease.