Dendritic cell based tumor vaccines

Dendritic cells (DC) constitute a unique system of cells that induce, susta in and regulate immune responses. Distributed as sentinels throughout the b ody, DC are poised to capture antigen (Ag), migrate to draining lymphoid or gans, and, after a process of maturation, select Ag-specific lymphocytes to which they present the processed Ag, thereby inducing immune responses. DC present Ag to CD4+ T cells which in turn regulate multiple effectors, incl uding CD8(+) cytotoxic T cells, B cells, NK cells, macrophages and eosinoph ils, all of which contribute to the protective immune responses. Several ke y features of the DC system may be highlighted: (1) the existence of differ ent DC subsets that share biological functions, yet display unique ones suc h as polarization of T cell responses towards Type 1 or Type 2 or regulatio n of B cell responses; (2) the functional specialization of DC according to their differentiation/maturation stages; and (3) the plasticity of DC whic h is determined by the microenvironment (e.g. cytokines) and may manifest a s (i) the final differentiation into either DC (enhanced antigen presentati on) or macrophage (enhanced antigen degradation); (ii) the induction of imm unity or tolerance; and (iii) the polarization of T cell responses. Because of these unique properties, DC represent both vectors and targets for immu nological intervention in numerous diseases and are optimal candidates for vaccination protocols both in cancer and infectious diseases. (C) 2000 Else vier Science B.V. All rights reserved.