Repetitive counterelectrophoresis on agar gel for the immunological identification of esterases produced by strains of Lancefield's group A, B, and C streptococci.

A method, repetitive counterelectrophoresis (RCE), was devised for detecting specific antibody to streptococcal esterase (STE). Reference antisera were prepared by immunizing rabbits with STE of streptococcal strains as follows: SS379 (group A, type 40), 69882 (group A, type 49), and H36B (group B, type Ib). Some human sera, derived from patients with scarlet fever, were also used as references. By this method, we have confirmed the immunological specificity of the STE produced by strains SS379 (STE-AI), 69882 (STE-AII), H36B (STE-B), and Austin (STE-C, group C) and have shown that the STE produced by strain 10706 (group C) is immunologically identical with STE-AI. Each STE presented a distinct colored line with the respective homologous antibody upon development of enzyme activity except for STE-AII, which formed a round spot with the homologous antibody. Horse activating factor (Hayano and Tanaka, 1973) formed a round spot with each STE. The factor in serum that reacted specifically with STE seemed to correspond to gamma globulin.