Investigations on cellular defense reactions with Galleria mellonella against Bacillus thuringiensis

In contrast to a great number of foreign particles (bacteria and inorganic materials), cells of some strains of Bacillus thuringiensis are not phagocytosed in the first hours after injection into the hemocoel of Galleria mellonella. This phenomenon is not caused by the production of β-exotoxin or exoenzymes, because heat-killed cells are not phagocytosed and the phagocytosis of latex particles is not prevented by the presence of living B. thuringiensis. The phagocytosis of heat-killed B. thuringiensis subtoxicus can be encouraged by treatment of the cells and by simultaneous injection of latex particles. A factor stimulating the phagocytosis is discussed. It is induced by the injection of phagocytosable latex particles into the hemocoel but not by injection of living or killed B. thuringiensis subtoxicus.