ANTI-ENZYME IMMUNITY 323 



a. Number of Pneumococcal Hemolysin Molecules Required to 

 Hemolyze One Red Blood Cell. The plasma of Luman blood amounts 

 to 55 per cent by volume; the cells make up the remaining 45 per cent. 

 There are 5X10^ red blood cells in one ml. of blood. One hemolytic 

 unit, H.U., of pneumomoccal hemolysin was defined by Cohen, Hal- 

 bert and Perkins (1941) as that amount of hemolysin capable of 50 

 per cent hemolysis of 4 ml. of a 1 per cent suspension of washed 

 red cells (or 2 ml. of suspension when complete hemolysis is con- 

 sidered). 



One ml. of whole blood contains 5X10^ r.b.c. Since 45 per cent of 

 the whole blood consists of red cells, 0.45 ml. of undiluted red cells 

 therefore contains 5X10^ r.b.c, or 1 ml. of undiluted red cells contains 

 1.11X10^° r.b.c. Two ml. of 1 per cent suspension of red cells should 

 therefore contain 1.11X101V100X2=2.22X10« r.b.c. Therefore 1 

 unit of hemolysin is capable of completely hemolyzing 2.22X10® r.b.c. 



The purest hemolysin contained 6000 H.U. per mg. Therefore 

 2.22X10^X6X10^=1.332X10^2 ^^^ ^^Iq^j ^eUg ^^^ hemolyzed by 1 



mg. of hemolysin. 



The data indicate that the hemolysin might have a molecular weight 

 of about 5X10^ in mg., or (5X10^ mg.=) 6.06X10^3 molecules. 



One mg. of hemolysin contains 1.21X10^^ molecules (6.06X10^^/5 



xioo. 



This shows that 9.09X10^ molecules O-2\X\0'V\ 332X10^^^ of 

 lysin are required for the hemolysis of one red blood cell. 



If we calculate the ratio of the weight of hemolysin to the weight 

 of red cells it hemolyzes we will have the follovvdng relationship. 



The sp. gr. of red blood cells is 1.1, or 1 ml. of red cells weighs 



1.1 g. 



One ml. of undiluted red cells, as shown above contains l.llXlO^*' 

 r.b.c. 



One r.b.c. weighs therefore iXlO'^^g. (=1.1/1.11X10^<'). 



One mg. of hemolysin hemolyzes 1.332X10^" r.b.c. 



One mg. of hemolysin hemolyzes 1.332X10^ g. (=1.332XlO'2x| 

 X10-io>) oj. 1.332X10^ mg. r.b.c. 



Since only 40 per cent of the r.b.c is total solids the ratio on a dry 

 weight basis is 133,200X0.4=53,280, or 1 : 53,280. 



However, if we consider the stroma of the red cells as a closer ap 

 proach to the true substrate, and since the stroma represents about 10 



