Abstract
The author has demonstrated that feeding the pneumococcus to white rats produces an increased resistance to the living organism. The acid killed intact cell, 1 the bile salt dissolved organism 2 and the mechanically disrupted pneumococcus 2 have been found effective as immunizing agents when administered by mouth. With the object of determining, if possible, the particular component of the pneumococcus cell responsible for the observed effect, a degraded avirulent form of the pneumococcus, presumably producing no soluble carbohydrate,† was fed and it was shown 2 that comparatively little increased resistance was developed.
Recently, a carefully prepared sample of the specific polysaccharide of Type I pneumococcus was obtained through the courtesy of Dr. Harry Sobotka.‡ Experiments have been performed in which this material was dissolved in N/15 HCl, mixed with cracker meal, and fed to white rats. When subsequently examined these animals were found to possess an increased tolerance to intraperitoneal injection of the virulent organism.
Several facts had previously been shown to characterize the immunity produced by feeding the bacteria, either whole or dissolved, and offered a means by which one might determine to what extent the results obtained by feeding the specific polysaccharide resembled those gotten when the bacteria were administered. These were: (1) the immunity is produced by a single feeding, (2) it is present 48 hours following such ingestion, (3) in extent it is usually equivalent to 1,000 to 10,000 fatal doses (Type I), (4) when exhausted it can be made to reappear by a new feeding.
Of a group of 13 rats fed one dose of 0.5 mgm. of soluble polysaccharide (per rat), 5 survived when tested 48 hours later. Among them were animals which received 1, 10, 100 and 1,000 fatal doses of pneumococci.
Get full access to this article
View all access options for this article.