The occurrence in the rabbit of an acute phase protein analogous to human C-reactive protein has been confirmed. The acute phase protein of the rabbit reacts with a special form of the pneumococcal somatic polysaccharide, designated Cx polysaccharide, in the same manner that the human C-reactive protein reacts with the classical C polysaccharide. The method of preparation and some of the properties of the Cx polysaccharide are described.
The rabbit Cx-reactive protein has been shown to be remarkably similar to human C-reactive protein in its general properties and in the conditions which govern its appearance in the blood. It has been obtained in crystalline form, and appears to be antigenically distinct from the proteins of normal rabbit serum.