BACTERICIDAL PROPERTIES OF BLOOD SERUM 161 



BQDQiJQ 



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In this table it is noticeable that, although there has been con- 

 siderable bactericidal action in the mixtures in which 0.005, 0.001, 

 and 0.0005 c. c. of antiserum were used, the mixtures in which as 

 much as 0.1 and 0.01 c. c. were present, and in which one would nat- 

 urally expect a still greater antibacterial action, the contrary occurred. 

 This surprising and curious phenomenon, showing that an excess of 

 antibody could ac- 

 tually be harmful 

 to the functiona- 

 tion of the bacteri- 

 cidal complex, was 

 explained by Neis- 

 ser and Wechsberg 

 by the following 

 reasoning. In tests 

 like the one given 

 above a limited 

 amount of bacteria 

 and a 1 e x i n has 

 been mixed with 

 the enormous 

 amount of anti- 

 body represented 

 in the immune 

 serum. Although 

 bacteria can absorb more of this antibody than is necessary for their 

 solution or destruction, nevertheless the higher concentration given 

 in the table will contain quantities of "amboceptor" so far in excess 

 of the amount that can be absorbed that much of it must remain 

 free in the fluid. Now this amboceptor, possessing a complemen- 

 tophile group, is able to anchor complement or alexin as well as that 

 which has become united with the bacteria. In consequence, there 

 being only a limited amount of complement, some of this is deviated 

 from the amboceptor-antigen complexes by the free amboceptor, and 

 is, in consequence, ineffective so far as bactericidal action is con- 

 cerned. In the higher dilutions of the antiserum, in which no such 

 excess is present, the complement will be concentrated upon the "at- 

 tached" or "anchored" amboceptor, and greater efficiency will result. 

 Graphically Neisser and Wechsberg express their idea in the figure 

 which we reproduce. 



As to the accuracy of the observations of Neisser and Wechsberg 

 there can be no question, and everyone who has occasion to carry out 



Angreifen" upon the unaltered cell, but there is evidence that this union 

 takes place after the cell has absorbed the antibody, and no satisfactory 

 evidence to show that the thermostable body is an intermediary, that is, forms 

 a link as conceived in the amboceptor idea. 



* v :- ' *t x .-.:-- 



COMPLEMENT DEVIATION AS CONCEIVED BY NEISSEE AND 



WECHSBERG. 



The complement being united to the unbound ambo- 

 ceptor is thereby deviated from the amboceptor, 

 which has gone into relation with the antigen. 

 (After Neisser and Wechsberg, Munch, med. Woch., 

 1901, p. 697.) 



