Abstract
One of us previously showed that the pneumococcus soluble specific substance exerted a specific antiphagocytic action on the blood in vitro. 1 This finding has since then been confirmed by others. 2 , 3 , 4 In vivo attempts, on the other hand, have not so far given similar striking results. By injecting Type II soluble substance together with an attenuated Type II pneumococcus in mice, Felton and Bailey 5 found that it exhibited an antagonistic effect on the defense of the animals or an actual increase in the virulence of the organism from 10-100 folds. We wish to record the results of a study along similar lines but with more striking effects.
The soluble specific substance employed in this work was prepared from a Type II pneumococcus according to the method of Heidelberger and Avery. 6 The chief organism used was a strain of a typical Type II pneumococcus, highly virulent for white mice, but relatively avirulent for rabbits.
Preliminary experiments with a modified method 7 for demonstrating growth-inhibitory and pneumococcidal action of the blood before and after the intravenous injection of Type II pneumococcus soluble substance, showed that while rabbit blood normally was capable of destroying large numbers of Type II pneumococci, blood taken after the injection of the substance had entirely lost this property.
The effect of the intravenous injection of the soluble substance on the course of pneumococcus bacteremia in rabbits was next studied. It was found that when a sublethal dose of the Type II pneumococcus was injected intravenously into normal rabbits, the organisms quickly disappeared from the blood stream; whereas in rabbits receiving soluble substance and similar amounts of pneumo-coccus culture, an increase in the bacteremia ensued and frequently terminated in the death of the animals.
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