CHAPTER XI 



NATURE, FORMATION, ACTION AND 

 MEASUREMENT OF ANTIBODIES 



Introduction. — When one reviews the basic facts that have 

 been established beyond reasonable doubt about the plasma pro- 

 teins, he discovers that an important one is missing, since no one 

 knows with certainty the source of these plasma proteins. The 

 immunologist usually defibrinates the blood and works with the 

 serum proteins wliich remain. These represent a virtual spectrum 

 of colloids ranging from the water-insoluble and soluble euglobu- 

 lins through the pseudoglobulins to the water-soluble albumins. 

 In the circulating plasma they probably represent a very complex 

 arrangement of colloidal particles varying in size, amount of 

 bound water, chemical content and structure, electrical charges, 

 etc., and play many roles in the body's economy. 



By adding sodium sulphate to the extent of 13, 17 and 21 per 

 cent to different portions of serum, Howe precipitated three frac- 

 tions of proteins which are called euglobulins, pseudoglobulin 1 

 and pseudoglobulin 2, respectively. The albumins remained in 

 solution but are precipitated by higher concentrations of sodium 

 sulphate. Others have separated the serum proteins into these 

 and additional fractions by other methods. The most recent and 

 perhaps the most successful one is that of Ti.selius, who separates 

 proteins into different fractions according to their rate of move- 

 ment between two electrodes. 



Antibodies. — In previous chapters attention has been called to 

 research indicating that the blood plasma is virtually a reservoir 

 of traces of reacting substances or groups having more or less 

 specific affinities for many red cells of the same and different 

 species, for various kinds of bacteria, lipoids or lipoid-carbo- 

 hydrate complexes and various bacterial poly.saccharides. These 

 specific reacting factors are called natural antibodies and the sub- 

 stances for which they have specific affinities are called either 

 antigens or partial antigens (haptens as Landsteiner calls them). 

 They are real antigens if they can stimulate some animal body 

 to produce specific antibodies and partial antigens or haptens if 



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