Fate of Orally Administered Specific Polysaccharide of Pneumococcus.

Abstract

The author reported that, following the ingestion of Type I pneumococcus polysaccharide, white rats possess an increased resistance to the homologous organism. 1 It consequently became of interest to learn something concerning the fate of this material when thus administered. Furthermore, the promptness with which immunity appears 2 after feeding the pneumococcus, suggested the oral administration of dead pneumococci in the early stages of human pneumonia as a therapeutic measure. It therefore became of importance to know whether the contained soluble specific substance enters the circulation. If it does, such a procedure would seem to be contraindicated, since it has been shown that the specific polysaccharide inhibits the pneumococcidal action of a normal serumleucocyte mixture. 3

Since the carbohydrate confers immunity when taken by mouth it seems reasonable to suppose that it is absorbed from the intestinal tract. Its polysaccharide nature would suggest, on the other hand, that its absorption as such is improbable.

The blood serum was examined for the polysaccharide of Type I pneumococcus following oral administration. Interfering sediments obtained when some rat sera are mixed with horse serum caused considerable difficulty in deciding whether a given precipitate was indicative of the presence of minute amounts of the polysaccharide or not. Preliminary incubation of the animals'sera and of the immune horse serum largely avoided such interference. By adding known amounts of Type I polysaccharide to rat serum, it was found that the presence of 1 part in a million in serum can be detected with a fair degree of confidence in the result. In the experiments in which quantities up to 6 mg. were fed, we have been unable to find definite evidence that the polysaccharide is present in a concentration of 1 part per million in serum. It seems that if it enters the circulation at all, the polysaccharide is present in a smaller concentration than this. Insufficient examinations have been done to say definitely whether or not it can be found in the urine. More work will be done with blood and urine. However, it is of interest to note that a large proportion can be found in the feces.