Polymorphonuclear leucocytes contain an enzyme which destroys the basophilic character of beat-killed pneumococci (R and S variants) and inactivates the type specific polysaccharide antigen of encapsulated cells. The same enzyme, however, fails to cause a disintegration of the bacterial cells, or to decompose the capsular polysaccharide itself.

The enzyme has been extracted from a number of animal tissues; it appears identical with a purified enzyme extracted from pancreatin and which decomposes yeast nucleic acid.

These facts are considered with regard to the failure of rabbits to produce the type specific carbohydrate antibodies when immunized with heat-killed encapsulated pneumococci by the intradermal route.

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