Protective immunity induced by tumor vaccines requires interaction between CD40 and its ligand, CD154.

Interactions between CD40 and its ligand, CD154 (CD40L, gp39), have been shown to play a central role in the regulation of humoral immunity. Recent evidence suggests that this ligand-receptor pair also plays an important role in the induction of cell-mediated immune responses, including those directed against viral pathogens, intracellular parasites, and alloantigens. The contribution of this ligand-receptor pair to the development of protective immunity against syngeneic tumors was evaluated by blocking the in vivo function of CD154 or by studying tumor resistance in mice genetically deficient in CD40 expression (CD40-/-). In the former case, anti-CD154 monoclonal antibody treatment inhibited the generation of protective immune responses after the administration of three potent tumor vaccines: irradiated MCA 105, MCA 105 admixed with Corynebacterium parvum adjuvant, and irradiated B16 melanoma cells transduced with the gene for granulocyte macrophage colony-stimulating factor. Confirmation of the role of CD40/CD154 interactions in tumor immunity was provided by the overt tumor susceptibility in CD40-deficient mice as compared to that in CD40+/+ mice. In this case, wild-type but not CD40-deficient mice could be readily protected against live TS/A tumor challenge by preimmunization with TS/A admixed with C. parvum. These findings suggest a critical role for CD40/CD154 interactions in the induction of cellular immunity by tumor vaccines and may have important implications for future approaches to cell-based cancer therapies.

Clinical experience with artificial liver support systems.

Fulminant hepatic failure is a devastating disease that, despite recent therapeutic advances, continues to be associated with high morbidity and mortality. Orthotopic liver transplantation has emerged as the sole modality of treatment that significantly improves survival. However, the critical shortage of donors precludes timely transplantation for all patients. Consequently, almost half of all patients with fulminant hepatic failure die before a graft becomes available. This has generated interest in developing a system that would support patients until either native liver regeneration occurs or an optimal donor liver can be found. Investigators have used biological, artificial and bioartificial techniques in an attempt to improve survival in liver failure. This article reviews the history, the current state of the art and future directions of artificial liver support.