COMPLEMENT FIXATION 185 



opinion is that the inhibiting action of serum is largely anti-com- 

 plementary in nature, although in part the action may be upon the 

 amboceptor. The great thermoresistance of the body in the serum 

 argues against the assumption of an anti-complement in the strict 

 immunological sense. The action may well be anti-complementary, 

 but from the work of Bordet and Gay, as well as of Noguchi, it would 

 appear that the concentration of colloids associated with a disturbance 

 of lipoidal balance or combination must occupy a most important place 

 in hypotheses concerning this phenomenon. Of practical importance 

 is the fact that prolonged preservation of serum increases its anti- 

 lytic capacity. 



Anti-hemolytic Activity of Immune Sera. In discussing the prop- 

 erties of complement (see page 137) we mentioned the experimental 

 evidence concerning the production of anti-lysins and anti-comple- 

 ments by the injection of immune and normal sera. The anti-lytic 

 activity of such immune sera was thought at first to be due to an 

 anti-complement, but later was thought to be the result of action upon 

 the amboceptor or sensitizer. It must be recognized, however, that the 

 injection of a serum, whether it contain complement or immune ambo- 

 ceptor, leads to the production of a precipitin and that such precipitins 

 can be demonstrated in the immune sera containing the so-called anti- 

 complement. As has been pointed out in the preceding discussion on 

 complement fixation the presence of precipitates serves to fix com- 

 plement and this probably accounts for the anti-lytic and anti-comple- 

 mentary powers of the immune sera. 



The fact that agglutination of the red cells inhibits their lysis was 

 pointed out independently by Handel and by Karsner and Pearce. This 

 renders inadvisable the use for complement-fixation tests of sera which 

 are strongly hemagglutinative. 



