The Effect of Type-I Pneumococcus Culture Broth on the Phagocytic Action of Type-I Pneumococcus Serum

Abstract

Summary In normal serum of the horse and rabbit, virulent pneumococci were not phagocyted. In the homologous immune sera, active phagocytosis took place. In the immune sera incubated with the culture broth of virulent pneumococci, centrifugalized or filtered, phagocytosis of virulent pneumococci was inhibited. This inhibitory action was apparently the result of reactions that took place during the incubation of the immune serum with the culture broth. In contrast to previous experiments with diphtheria and other culture broths, the inhibiting action of which was apparently the result of adsorption of the inhibitory substance on the leucocyte, in these later experiments the exposure of the leucocytes to the pneumococcus culture broth failed to give uniform results. Phagocytosis of sensitized S. pyogenes aureus not only varied greatly but, in some instances, was apparently more active than with leucocytes not exposed to the pneumococcus culture broth. Inhibition of phagocytosis of pneumococci was much more pronounced when the serum was exposed with the culture broth before the leucocytes were added, and the degree of inhibition varied with the concentration of the serum. Inhibition was obtained with eighteen-hour broth cultures and in greater degree with cultures which had been incubated twenty days. The inhibitory action was not increased by exposure of the culture broth with the serum for more than one hour. Preliminary exposure at 41° and 44°C. instead of at 37°C. did not appear to increase or decrease the action of the inhibitory substance. Heating for thirty minutes at 75°C. or for five minutes at boiling did not diminish the inhibitory action of the culture broth. No inhibition of phagocytosis of virulent pneumococci occurred with eighteen-hour culture broth of an attenuated type-I pneumococcus. Slight inhibition was obtained when a thirteen-day culture broth of the attenuated strain was used. Sodium-oleate extracts of washed virulent pneumococcus cells had a similar but more marked inhibitory action as compared with the culture broth. Apparently the action of these extracts was, in some degree, type specific: that is, type-I extract with type-I serum inhibited phagocytosis of type-I organisms but not of type-III pneumococci in type-III serum, whereas type-III extract with type-I serum failed to inhibit phagocytosis of type-I cells.