OPSONIC ACTION 167 



In this case there is, however, a complication, inasmuch 

 as the bacteria alone absorb a certain amount of complement. 

 We accordingly treat another sample of serum with bacteria 

 only, this being done in exactly the same way, with the 

 single difference that the bacteria are not previously treated 

 with immune-body. 



The following experiment is an example of the different powers of 

 absorbing hsemolytic complement possessed by treated (sensitized) 

 and untreated bacteria respectively. A test of this kind was always 

 employed before their effect on opsonin was estimated. 



Three series of tubes are prepared. Each receives 0-05 c.c. of 

 emulsion of a culture of B. coli. 



To the first series (a) no anti-serum is added. 



To the second series (6) 0-001 c.c. anti-serum is added. 



To the third series (c) 0-01 c.c. anti-serum is added. 



To the several tubes in series increasing quantities of guinea-pig's 

 complement are added. The contents are made up to 1 c.c. with 

 salt solution, and the tubes are placed in the incubator for one and 

 a half hours to allow combination of complement to occur. To each 

 tube 1 c.c. of a suspension of ox's corpuscles (sensitized) is added 

 to test for free complement. Complete lysis is got in the different 

 series with the following amounts of added complement : 



Emulsion alone . . . 0-03 c.c. 



Emulsion + 0-001 c.c. anti-serum, 0-075 c.c. 



Emulsion -f 0-01 c.c. 0-125 c.c. gives lysis. 



The hsemolytic dose of untreated complement was 0-015 c.c. 



It is thus shown that, while the bacteria alone take up a certain 

 amount of complement, the addition of immune-body (anti-serum) 

 leads to the taking up of much more. How is the opsonic effect 

 influenced ? The following examples show this clearly. 



We shall call the serum treated with bacteria + immune-body 

 Serum A, and the serum treated by bacteria alone Serum B. 



Anti-serum to B. coli 



Treated Serum A = 1 c.c. of guinea-pig's serum treated with 

 0-25 c.c. emulsion of B. coli + 0'05 c.c. anti-serum (immune-body). 



Treated Serum B = 1 c.c. of guinea-pig's serum treated with 

 0-25 c.c. emulsion of B. coli alone. 



The organisms were killed by heat before being used. 



