A cell-wall carbohydrate consisting of N-acetylglucosamine, N-acetylgalactosamine, galactose and rhamnose was isolated from group L hemolytic streptococci. The antigenic determinant of this carbohydrate consisted of terminal β-N-acetylglucosamine residues attached to rhamnose side chains of the polymer. Group L carbohydrate treated with an induced enzyme preparation from a soil bacterium no longer gave a precipitin reaction with its homologous antiserum but did so strongly with antigroup G streptococcal serum. The native carbohydrate also gave a precipitin reaction with antisera from rabbits immunized with group A streptococci. The antigenic cross-reactivity between group A and group L carbohydrates was due to the fact that the antigenic determinants of both carbohydrates were terminal β-N-acetylglucosamine residues. The N-acetylglucosamine residues of group L carbohydrate were extremely acid labile, whereas those of the group A carbohydrate were considerably more stable. This difference indicated some subtle structure differences between group A and group L antigens.
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Karakawa et al. (1971) studied this question.