Studies in immunization by a species antigen: I. Preparation of species antigen from pneumococci

Abstract

From pneumococci a species antigen can be obtained which on injection gives protection against pneumococci of different types.Species antigen is a somatic constituent of pneumococci and can be obtained in solution free of protein. It may be of carbohydrate nature, but is not derived from the type-specific material.The bodies of pneumococci contain another substance which on injection opposes species immunization. This opposition factor is closely associated with the protein content.Inconstant results from injection of preparations containing species antigen are due to the presence of opposition factor in varying amount.A high degree of species immunity can be secured by the use of species antigen freed from opposition factor.