Interaction of cancer chemotherapy agents with the mononuclear phagocyte system

Cytotoxic agents used in the medical treatment of neoplasia have profound effects on host immunity. Traditionally the interaction of cancer chemotherapy agents with immunity has been considered in connection with immunodepression. Immunodepression is in fact a prime determinant in the pathogenesis of some of the acute and longterm toxicities associated with cancer chemotherapy, including infections and second malignancies. Interference with immunity has also been considered an intrinsic limiting factor in the efficacy of anticancer agents. In this perspective, chemotherapeutic agents are, in a way, self-defeating. More recently, evidence has accumulated that the interaction of cancer chemotherapeutic agents with immunity is more complex than originally envisaged and that these drugs should be considered from the wider perspective of immunomodulation rather than from the narrower angle of simple immunodepression. In this light, it appears that the relationship between antitumor efficacy and modulation of host resistance is more complicated than expected on the somewhat simplistic assumption that chemotherapeutic agents act as pure depressants of immunity and that no substantial differences exist among antitumor drugs in their interaction with host defence mechanisms.