ANTI-ENZYME IMMUNITY 



327 



of opalescence was observed after incubating a strong solution of 

 streptolysin for 24 hours at 38° with the lecitho-vitellin solution. 



The purified streptolysin O preparations were toxic to mice on in- 

 travenous injection. The minimum lethal dose was about 135 H.U. 

 or 0.044 mg. of the preparation. The streptolysin O had a much 

 greater lethal effect when injected in an activated form, e.g. together 

 with cysteine, although cysteine alone had no harmful effect. The 

 authors suggested that in vivo its action is similar to that in vitro. 



Streptolysin O was stated to be different from the erythrogenic toxin, 

 streptolysin S, leucocidin, fibrinolysin and the diffusing factor (hyalu- 

 ronidase). 



It was inactivated by oxidation, and the inactivation was reversed 

 by all the compounds containing the -SH group. Compounds con- 

 taining the -S-S- group, ascorbic acid and ferrocyanide had no activat- 

 ing effect at all. A medium degree of activation was achieved by potas- 

 sium cyanide and sodium thiosulfate. These facts suggested that the 

 hemolysin molecule containing the -SH group is active; its oxidation to 

 the -S-S- group inactivates it. This confirmed the observations by 

 Smythe and Harris (1940). 



The hemolytic activity was greatest at pH 6.5 and decreased mark- 

 edly on both sides of this optimum pH. The optimum temperature of 

 the hemolytic activity was 38°. At 0° the activity was 3 per cent of the 

 optimal activity. 



At 0° hemolysin adsorbs on red cells without hemolysis for half an 

 hour. The supernatant of the centrifuged cell-hemolysin mixture is 

 free from hemolysin. On suspending the centrifuged cells in fresh 

 saline and incubating at 38°, they are rapidly hemolyzed. The results 

 were interpreted to show that the adsorption of streptolysin on the 

 red cell surface is a different reaction from the actual process of lysis, 

 in which a chemical process is probably involved, since it is inhibited, 

 while adsorption processes are increased, by low temperatures. 



According to Herbert (1941) when small amounts of hemolysin 

 were added to the system only a small percentage of the red cells pres- 

 ent were hemolyzed; the smaller the number of red cells present, the 

 greater the amount of hemolysis. This means that for each individual 

 red cell, a certain critical amount of streptolysin must be adsorbed on 

 its surface to cause hemolysis in a given time (see the discussion on 

 pneumococcal hemolysin); if less than this amount is present, no 



