Abstract
Our recent communication 1 which described a high grade of localized antistreptococcus protection in the pleural cavity of the rabbit induced by the previous injection of indifferent, non-antigenic substances, left in question the relation of this protection to a specific immunity which might be produced by the streptococcus. A thickened granulating parietal pleural wall containing large numbers of phagocytic clasmatocytes is produced by the inoculation three days previously of gum arabic broth or aleuronat-starch and such a cavity resists infection by many multiples of the normally fatal dose of our pathogenic streptococcus. The duration of this protection is from ten days to two weeks and its disappearance is paralleled by a return of the pleural wall to approximately its original condition as we have learned from recent histological study.
Repeated injections of the original non-specific substance, or of considerable doses of the streptococcus in the second and subsequent inoculations, produced further thickening of the pleural wall, an increased number of cells, and an apparently still more marked resistance to the streptococcus. In other words, there was an indication that the degree of resistance varies directly with the number of clasmatocytes present in the protected area. We at once raised the question, however, of the significance of specific antibodies, whether localized or general, in conditions of this sort. In other words, will granulation tissue of a given thickness produced by gum arabic broth afford as much protection as an equal accumulation of cells produced by the streptococcus? A preliminary experiment which we published seemed to answer this question in the negative but was not regarded as conclusive, owing to certain technical difficulties involved.
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