Emanuel Suter

CELLULAR REACTIONS IN INFECTION.

Publisher Summary Cellular reactions are involved primarily or secondarily in host-parasite relations, that is, either as a response to direct stimulation by the pathogen or its products or mediated by factors liberated in the primary reaction. The chapter discusses the killing of parasites by phagocytic cells and the evidence for the existence and importance of mononuclear phagocytes having an enhanced capacity to destroy intracellular parasites, apart from recognizable assistance by specific antibodies. The possible connection between such cellular immunity and delayed-type hypersensitivity is a matter of great practical interest. The normal phagocyte in post-engulfment period (influence of particle ingestion on metabolic activity, intracellular kill of microorganisms, digestion of intra-cellularly killed bacteria, and facultative intracellular parasites) and the immune phagocyte such as demonstrations of cellular immunity, in vitro acquisition of cellular immunity, properties of the immune mononuclear phagocyte, nonspecific manifestations of cellular immunity, consequences of residence in immune cells, transfer of cellular immunity, relationship of cellular immunity and delayed-type hypersensitivity, and the immune cell in reactions to tissue and cellular homografts are also discussed. The chapter also discusses chemotaxis and phagocytosis such as opsonins, virulence, and opsonization.

Sensitivity of Mice to Endotoxin after Vaccination with BCG (Bacillus Calmette-Guérin).

Summary 1. It is shown that a single intravenous injection of BCG in mice induces a state of hyperreactivity to bacterial endotoxin. The LD50 for E. coli lipopolysaccharide is decreased from 357 μg in controls to 6 or 7 μg in BCG vaccinated animals. This change appears around the 5th day after vaccination. 2. Trehalose dimycolate, a component derived from virulent tubercle bacilli induces a similar state of hyperreactivity to endotoxin upon single or repeated injections.

NONSPECIFIC AND SPECIFIC CELLULAR REACTIONS TO INFECTIONS

During the last few years it has become increasingly evident that the response to antigenic stimulation by bacterial components or bacterial infection is not limited to antibody production. A number of reaction mechanisms other than circulating antibodies are acquired by the host as a consequence of such stimulation. Thus functional versatility is added to existing humoral and cellular mechanisms representing the host’s capacity to respond to stimulation. Some of these changes are specific for the agent used for induction, whereas others are nonspecific in character. Frequently alterations of the host’s resistance to infection with antigenically related or unrelated pathogens are associated with these changes. Observations concerning alterations of nonspecific resistance to infection and the adaptive capacity of the RES under various conditions have been reviewed recently.’** In view of such findings, a consideration of the host’s total capacity to respond to primary and secondary infection has come within reach. Also, a separation into humoral and cellular reactions is desirable. However, difficulties are encountered when alterations on a cellular level are considered. First, quantitative information is scarce, partially due to the lack of techniques allowing accurate measurements with single cells. Second, it is extremely difficult, if not impossible, to obtain homogeneous populations of cells that belong to a widely distributed system such as the RES without introducing procedures that by themselves act as nonspecific or specific stimuli. Third, analysis of experimental results is hindered by the fact that the contributions of the extracellular environment cannot be excluded either in in vitro or i n vivo experimentation. In the following some cellular reactions induced by infection with tubercle bacilli are reported.

Transitions in Basic Medical Science Teaching

This chapter will trace changes in the goals, instruction and governance of basic science education over the last century. In the first half of the 20th century basic science departments organized by discipline (e.g. anatomy, physiology, pathology) and did their best to teach medical students the basic science facts and concepts which basic science faculty thought were necessary for the practice of medicine. This included utilizing the scientific method to solve problems relative to their discipline. By the end of the 20th century, in some medical schools the basic science content was being defined by interdisciplinary groups and taught in more integrated ways with the expectation that this would enable students to be better able to recall, integrate and utilize their basic science knowledge in clinical situations. Research which suggested that problem solving skills are less generalizable than originally thought, promoted the teaching of problem solving in each discipline or sub-discipline, e.g. gastroenterology and nephrology.

Effect of BCG Infection on Sensitivity of Mice to Histamine, Serotonin and Passively Induced Anaphylaxis.∗

Summary BCG infection, although previously shown to increase the sensitivity of mice to endotoxin, does not increase the sensitivity of mice to passively induced anaphylaxis to histamine or to serotonin. Heparin, which inhibits the Shwartzman reaction in rabbits, failed to prevent endotoxin hyperreactivity in BCG-inoculated mice.

Endotoxic Activity of L-Forms derived from Salmonella paratyphi B..

Summary L-forms derived from S. paratyphi B are 5.5 to 9.0 times less toxic than their parent bacterial form. Their toxicity remains relatively constant during successive transfers in the L-state.