REACTIONS OF RABBITS TO INTRACUTANEOUS INJECTIONS OF PNEUMOCOCCI AND THEIR PRODUCTS

Abstract

60 rabbits were immunized by repeated injections into the skin, of small doses of suspensions of heat-killed type I pneumococci. In 53, no type-specific antibodies appeared in the serum; in the remaining 7, the titer was very low. In all cases, however, the sera possessed a high titer of species-specific antibodies. 45 rabbits similarly immunized by injections of heat-killed type III pneumococci also formed species-specific antibodies, and failed to form type-specific antibodies. Suspensions of heat-killed R pneumococci and solutions of bacterial substances, when injected into the skin, stimulated production of species-specific antibodies, although they failed to stimulate production of type-specific antibodies. Animals immunized by intracutaneous injections were still able to form type-specific antibodies when subsequently given intravenous inoculations of type-specific pneumococci.