106 ANTIBODIES AND OPSONINS. 



researches along the line of haemolytic reaction, found that 

 under certain conditions haemolysis was prevented, and this 

 so-called Bordet-Gengou phenomenon has been the starting- 

 point of the many complement deviation reactions. The prin- 

 ciples proved by Bordet and Gengou are that a substance 

 which produces antibodies, which they call an antigen, when 

 mixed with an antiserum or serum immunized against it, and 

 complement added, this complement is bound by the antigen 

 and the arnboceptor (antibody) and rendered inert. To prove 

 this and to finish the reaction, red blood-cells and a known 

 haemolytic serum are added to the mixture after it has been 

 allowed to remain in the incubator for one hour at 37.5 C. 

 The haemolytic serum must have been inactivated by heating 

 to 56 C. before it was added, that is, its complement must be 

 destroyed. If the serum being tested contains the specific 

 amboceptors and is rendered inert as described above, the 

 complement, being used up or deviated, will not be available 

 to complete the haemolytic unit, and no haemolysis will take 

 place. If, on the contrary, the serum mixed with the antigen 

 be not its specific antiserum, the complement will not be 

 bound, and, being therefore available in the second part of 

 the test, will complete the combination of corpuscles haemo- 

 lytic serum and complement, and haemolysis will take place. 

 By reversing this reaction with a known serum, antigen can 

 be determined. It must be remembered as an essential prin- 

 ciple that amboceptors or antibodies alone or antigen alone 

 cannot bind complement, but together they can, when specific 

 for one another. The Wassermann reaction is simply an 

 application of these principles. It will be described under 

 the heading of Treponema Pallida. 



This test is applicable to any form of bacteria, emulsions 

 of cultures being used as antigen. 



OPSONINS. 



Opsonins were first named and their properties described 

 by Wright. He claimed for them an independent identity, 

 while other observers have since classed them as identified 

 with serum complement. Both views have numerous cham- 



