The host-tumor immune conflict: from immunosuppression to resistance and destruction.

A successful immune response against a tumor is dependent on the cytokine repertoire present at the tumor site. Salem Chouaib and colleagues discuss evidence that, to escape the immune system, tumor cells not only produce immunosuppressive cytokines but also employ strategies involving altered susceptibility to tumor necrosis factor and Fas cytotoxic pathways and, in some circumstances, use of the Fas ligand to neutralize effector cells.