294 ANAPHYLAXIS 



Summary of Immunity as Applied to Protection 

 FROM Disease. 



The discussion of "immunity problems" in the preceding 

 chapters serves to show that protection from disease either 

 as a condition natural to the animal or as an acquired state 

 is dependent on certain properties of its body cells or fluids, 

 or both. The actual factors so far as at present known may 

 be summarized as follows : 



1. Antitoxins which neutralize true toxins; shown to exist 

 for very few diseases. 



2. Cytolytic substances which destroy the invading organ- 

 ism: in reality two substances; amboceptor, which is spe- 

 cific, and complement, the real dissolving enzyme. 



3. Phagocytosis or the destruction of the invading organ- 

 isms within the leukocytes. 



4. Opsonins which render the bacteria more readily 

 taken up by the phagocytes. 



5. Enzymes other than complement possibly play a part 

 in the destruction of some pathogenic organisms or their 

 products. This remains to be more definitely established. 



6. It is possible that in natural immunity there might 

 be no receptors in the body cells to take up the organisms 

 or their products, or the receptors might be present in 

 certain cells but of a very low chemical affinity, so that com- 

 bination does not occur. It is even highly probable that 

 many substances formed by invading organisms which might 

 injure specialized cells, such as those of glandular, nervous 

 or muscle tissue, have a more rapid rate of reaction with, or 

 a stronger affinity for, lower unspecialized cells, such as con- 

 nective and lymphoid tissue, and unite with these so that 

 their effects are not noticed. 



The importance of these different factors varies in differ- 

 ent diseases and need not be considered in this connection. 



The question "which of the body cells are engaged in the 

 production of antibodies" is not uncommonly asked. On 

 physiological grounds it would not seem reasonable that the 

 highly specialized tissues above mentioned could take up 



