Pre-treatment with Concanavalin-A increases resistance of mice to peritoneal infection by Serratia marcescens.

Mice pre-treated with Concanavalin-A largely survived an intra-peritoneal inoculum of 2 x 10(7) Serratia marcescens, whereas all control mice died within 15 h of inoculation. A subpopulation of peritoneal macrophages from Con-A pre-treated mice was able to phagocytose the bacteria in vitro (6.7 SEM 1.2% phagocytosing cells) and in vivo (16.9 SEM 2.1%), whereas control phagocytes did not phagocytose S. marcescens. The survival of Con-A pre-treated mice allowed their immunisation with living bacteria, and the antiserum thus produced increased the phagocytosis of S. marcescens in vitro. Control mice largely survived an inoculum of S. marcescens suspended in 50% immune serum, although the bacteria were resistant to the bactericidal activity of that serum. These results suggest that, in contrast to the delayed humoral protection afforded by immunisation, phagocytosis by phagocytes activated by Con-A conferred early protection to mice against experimental infection by S. marcescens.

Hemolytic activity of Trichomonas vaginalis and Titrichomonas foetus

The hemolytic activity of live isolates and clones of Trichomonas vaginalis and Tritrichomonas foetus was investigated. The isolates were tested against human erythrocytes. No hemolytic activity was detected by the isolates of T. foetus. Whereas the isolates of T. vaginalis lysed erythrocytes from all human blood groups. No hemolysin released by the parasites could be detected. Our preliminary results suggest than hemolysis depend on the susceptibility of red cell membranes to destabilization and the intervention of cell surface receptors as a mechanism of the hemolytic activity. The mechanism could be subject to strain-species-genera specific variation of trichomonads. The hemolytic activity of T. vaginalis is not due to a hemolysin or to a product of its metabolism. Pretreatment of trichomonads with concanavalin A reduced levels of hemolysis by 40 por cento.