SENSITIZING ANTIBODIES 295 



antibodies, including the so-called amboceptors or sensitizers that 

 take part in the phenomena of lysis and bactericidal action are 

 essentially of one type; that the fundamental phenomenon is the 

 union of the antigen with the specific antibody or its "sensitiza- 

 tion;" that by such sensitizatioii the antigen is now rendered on 

 the one hand more easily agglutinable or precipitable, on the other 

 may be rendered more amenable to the action of the alexin or com- 

 plement or to phagocytosis. The agglutination and precipitation 

 phenomena, moreover, are merely evidences of the fact that these 

 substances are in colloidal suspension and are influenced by agencies 

 which produce precipitations in such suspension. It is interesting 

 to note in this connection, also, that bacteria in neutral suspension 

 carry negative charges which can be weakened by sensitization with 

 serum and weakened or reversed by the addition of acid. These 

 points tend to strengthen such a point of view. 



The degree of acidity necessary to reverse the normal negative 

 charge of bacteria corresponds roughly to that at which growth is 

 inhibited. This has led us to speculate whether or not vitality of 

 bacteria and the negative charge may be related. 



Facts Concerning Alexin or Complement. Muir and Browning 

 claim that, on the filtration of serum, amboceptor or immune body 

 will pass through the filter, whereas alexin or complement is held 

 back. 



This retention of complement by filters occurs only when new 

 filters are used, and this is probably due to adsorption or comple- 

 ment by the finely divided substances which make up the filter and 

 not due to retention because of the large size of the complement 

 molecule. 



Alexin can be inactivated by shaking as well as by heat when 

 diluted 1 :10 and shaken for about 20 minutes in salt solution. Ac- 

 cording to Gramenitski it is spontaneously partially reactiviated 

 on standing. 



Alexin is dependent upon the total volume of the mixture in 

 which it acts, i.e., upon concentration, the same actual quantity of 

 complement acting more strongly in higher than in lower concen- 

 trations, this not being true of amboceptor or sensitizer which acts 

 in direct proportion to its actual quantity independent of the con- 

 centration. 



Alexin is inhibited by hypertonic salt solution and can be pre- 

 served in 15-25 per cent salt concentration for weeks in the icebox, 



