Matalová E., A. ·panová, F. KováfiÛ, M. Heroldová: Apoptosis Activation in Pig Leukocytes after Phagocytosis of Salmonella typhimurium. Acta Vet. Brno 2000, 69: 11-15. In this study we examined the effect of phagocytosis of living bacteria on apoptotic changes of DNA in pig leukocytes. The aim of this work was to observe how phagocytosis and killing of microorganisms can influence the survival of pig leukocytes. Blood samples were cultivated with suspension of Salmonella typhimurium LB 5000 up

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... o 48 h at a temperature of 37 °C. In the experimental groups, killed bacteria and microspheric particles, respectively, were used to determine the influence of the phagocytic process itself. In given intervals, samples of cultivated cells were taken for DNA analysis. DNA ladder assay was used for qualitative apoptotic DNA breaks detection by gel electrophoresis and TUNEL AP test for quantification of apoptotic changes. Cell morphology was observed after May-Grünwald Giemsastaining under light microscope. Spontaneous DNA degradation in the control group was observed after 8 h. In contrast, cells cultivated with microspheric particles or killed bacteria became apoptotic as soon as after 4 h. already. In the group exposed to living bacteria the apoptotic DNA degradation was slowed down and detected after 48 h mainly, while the other groups showed features of necrosis. These results suggest that the process of phagocytosis itself activates the apoptotic programme in phagocytic cells of the pig immune system but the presence of phagocyted living bacteria can delay this activation.