Abstract
In the preceding paper (Kusama et al., 1958) on the spectrophotometric determination of the hemolytic activity of streptolysin O (SL), the effects of red blood cell concentration, cysteine concentration, stabilizing agent and incubation time on the hemolytic activity were investigated, and the standardized conditions for the measurement were established.
The present study deals with the neutralization reaction of SL by antistreptolysin O (ASL) in human, horse and immunized rabbit sera, under various experimental conditions. Several methods have been reported for the ASL titration of human sera by other workers (Todd, 1932; Hodge and Swift, 1933; Coburn and Pauli, 1935; Ipsen, 1944; Rantz and Randall, 1945; Kalbak, 1947; Robinson, 1951; Halbert, Swick and Sonn, 1955) . Most of them employed 15 minutes at 37°C for the combination of SL with ASL, and 45 minutes for hemolysis, using the complete inhibition of hemolysis or partial hemolysis (especially 50% hemolysis) as the end-point. Experiments to be described in this report were conducted mostly by testing varying amounts of serum against a constant dose of SL. Extensive investigations on such variables as the time for SL-ASL combination and the amount of the test dose of SL revealed the qualitative difference of ASL in sera from patients with streptococcal infections as well as those from healthy persons. Our standard ASL was produced by an improved method of titrating the ASL in human sera, being devised to overcome the difficulty due to this qualitative difference.
