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Three of 64 IgA immunoglobuilins, derived from plasma cell tumors induced by mineral oil in BALB/c mice, precipitated with species-specific pneumococcus C polysaccharide. A related antigen was also found in group O and some group H streptococci. A difference in ability to precipitate a C polysaccharide from a pneumococcus type XIV was demonstrated between protein 603 which did precipitate and protein 167 which did not precipitate this polysaccharide. Studies of the 167 and 603 proteins showed differences in electrophoretic mobility and polypeptide chains. The antigen-combining site of the 167 and 603 proteins resided on the papain-digestion Fab fragment.
Potter et al. (Fri,) studied this question.