The subject matter of this volume, the basis for which was a conference held in Philadelphia which focused on the subject of infections, including their diagnosis and treatment, in immunocompromised individuals. The material is of particular importance today when placed against the background of the rapid spread of acquired immunodeficiency syndrome (AIDS). The first section dealt with the general subject of the immunocompromised host. Here, reviewed in detail, were the epidemiological and clinical aspects of opportunistic infections in patients with defective immune responses. It is widely acknowledged that infections are a major complication of the neoplastic process. Cancer-bearing patients are more prone to certain kinds of infectious and cancer chemotherapy almost always increases susceptibility to such infections. Depending upon the basic disease process of the cancer, a specific array of infectious diseases can be predicted. Patients altered in thymus-derived lymphocyte populations or mononuclear phagocyte capabilities resulting in defects in cell mediated immunity or delayed hypersensitivity become highly susceptible to certain groups of organisms, whereas, profoundly neutropenic patients usually become infected with different organisms. The types of infections noted are relatively predictable for the type of immune defect, with some variations according to epidemiological factors. Major advances have been made in the early diagnosis and treatment of infectious complications with increasingly effective antimicrobial agents and increasing knowledge of their use. The application of so-called preventive procedures has had limited value to date, including immunotherapy, which appears to hold much promise.

The subject matter of this volume was the basis for a confer ence held in Philadelphia in June, 1981, and is an important one in the contemporary area of how the host interacts with micro organisms. In conception, it grew out of a graduate course entitled, "The Infectious Process," which has been taught in the Department of Microbiology and Immunology at Temple University School of Medicine during the past twelve years. This course has explored the broad areas of mechanisms of microbial pathogenesis and host resistance by in-depth consideration of selected models of experimental infection and immunity, as well as the clinical literature. It is noteworthy that there is no adequate text for this material, as the subject matter naturally crosses a wide spectrum of traditional disciplinary lines, encompassing topics as diverse as the mechanisms of action of bacterial toxins, the role of complement and antibody in phagocytosis, and the importance of cross-reacting bacterial polysaccharide antigens in vaccine development. A major portion of the course has always considered "cellular immunity" as it applies to host defenses to intracellular pathogens. It is in this area that the necessity for amalgamation of information from different disciplines is most evident, for one must be intimately concerned with the interactions between the microbe and the phagocyte, both before and after specific immune recognition."