232 MECHANISM OF HAEMOLYSIS 



(v) If the foregoing experiment be repeated and instead of rabbit cells, 

 red cells of some other animal, sheep, for instance, be added to the heated 

 haemolytic serum it can be shown that the sheep cells are not sensitized, 

 since on the addition of complement they are not haemolyzed. 



And further, the serum to which the sheep cells have been added has 

 retained intact its sensitizing properties and is still capable of sensitizing 

 rabbit red cells. 



This experiment again demonstrates the specific nature of the reaction. 



(vi) Haemolysis does not occur at C. Place a mixture of non-heated 

 hsemolytic serum and a suspension of the corresponding red cells in the ice 

 chest for several hours, then centrifuge the mixture and wash the cells in 

 the cold, add some complement to the cells and incubate at 37 C. : haemo- 

 lysis occurs. Add the serum to some sensitized and washed red cells and in 

 this case also haemolysis occurs. In other words the immune body has been 

 taken out of the serum by the red cells but ,at the temperature of the experi- 

 ment the complement remains in solution. 



Conclusions. 



When a living animal is treated with sublethal doses of micro-organisms 

 or their toxins (antigen) a substance inimical to the antigen (antibody, 

 amboceptor, sensibilisatrice, immune body) appears in the serum which has 

 the property of combining with the antigen, thus rendering the latter 

 susceptible to the action of a third substance (complement, alexin, cytase) 

 already present in the serum of the normal animal and derived probably 

 from the leucocytes. 



By the combined action of the immufte body and complement, the antigen 

 is either destroyed (in the case of red cells or delicate organisms) or prepared 

 for the destructive action of the leucocytes (as happens with micro-organisms 

 in general). 



The fixation of the complement. 



(Deviation of the complement.) 



Prepare in accordance with the rules elaborated in the preceding para- 

 graphs the following experiment. 



Mix in suitable proportions a portion of a culture of the cholera vibrio and 

 some anticholera serum previously heated at 55 C., incubate for 1 hour, and 

 then add a small quantity of non-heated serum (complement) to the mixture. 

 Under these 'conditions the vibrios sensitized by the specific immune serum 

 are bacteriolyzed by the action of the complement. Now add to the mixture 

 some red cells sensitized with their corresponding inactivated immune serum 

 (hcemolytic couple) ; no haemolysis takes place because there is no complement 

 available, the complement originally present having all been used up in pro- 

 ducing bacteriolysis of the cholera vibrios. In other words there has been 

 fixation, or deviation, of the complement by the sensitized vibrios. 



Now perform a second experiment. Mix a portion of a culture of the 

 typhoid bacillus with some inactivated anticholera immune serum and after 

 incubating, add a small quantity of guinea-pig complement. In this case, 

 the immune body has not been able to sensitize the bacilli being specific for 

 and combining only with cholera vibrios : consequently, the complement 

 remains unattached, in other words, is not deviated. Now add some sensitized 

 red cells to the mixture and incubate again ; haemolysis of the red cells occurs 

 because there was free complement in the mixture with which they were able 

 to combine. 



From this fundamental experiment Bordet and Gengou deduced a very 



