144 LIFE: ITS NATURE AND ORIGIN 



process long in commercial use for making certain dyes or colors; 

 thus para red is made by diazotizing p-nitraniline and adding 

 beta-naphthol. 10 



Landsteiner found that his newly synthesized protein addition 

 compounds could evoke the formation of specific antibodies, but 

 that the specificity depended largely upon the nature of the mole- 

 cule attached, which he termed the hapten. While haptens, of 

 themselves, are unable to cause antibody formation, when they are 

 attached to the protein they determine to a large extent the 

 specificity of the antibody formed.* The fact that haptens which 

 are very similar chemically, interact serologically ("cross-reac- 

 tions"), supports the view that the specificity of antibodies and of 

 antigens is determined by their outwardly directed electronic 

 fields, which naturally vary with change in chemical and physical 

 structure. 



Reactions Between Antigens and Antibodies 



Most immunological reactions fall into one of the following 

 groups: 



(1) Toxin-antitoxin neutralization: If properly made, a mix- 

 ture of toxin and its specific antitoxin is innocuous. A toxin 

 formed in or introduced into an animal can be neutralized by its 

 specific antibody, if administered in time. Thus diphtheria anti- 

 toxin must be given before the diphtheria toxin, produced by 

 the invading bacteria, has been irreversibly fixed by certain nerve 

 cells in the medulla. Death from paralysis of the heart and the 

 respiratory system may follow injury to these cells, and even in 

 cases that recover, temporary paralysis of the limbs may occur. 

 Injections of toxoid or of toxin-antitoxin mixtures are now gen- 

 erally used to establish immunity to diphtheria. As far back as 

 1909, Dr. J. G. M. Bullowa and the writer followed in the ultra- 

 microscope the mutual coagulation of diphtheria toxin by diph- 

 theria antitoxin and of tetanus toxin by tetanus antitoxin. But 

 neither toxin formed a coagulum with the antitoxin specific to 

 the other one. 11 



(2) Precipitin reactions: When a suitable amount of a soluble 

 antisren is mixed with the blood serum of an animal immunized 

 by injections of this particular antigen, a precipitate appears, and 

 generally is visible. This is known as the Ramon test. 12 



(3) Agglutination reactions: When an antigen having visible 



* This recalls the action of prosthetic groups in enzymic catalysts. 



