94 IMMUNOLOGV 



When one injects a cellular antigen into the animal body, the 

 antigen is rapidly removed from the point of injection and ap- 

 pears in the blood stream. From the latter it is removed by 

 phagocytic cells of the reticiilo-endothelial system. If one uses 

 an antigen such as avian red cells which can be readily identified 

 microscopically, one can trace these to the Kupffer cells of the liver 

 and fixed tissue cells of the spleen, lymph glands, etc., by studying 

 properly prepared sections of these tissues. After an interval of 

 several days, specific antibodies for avian red cells, or the particu- 

 lar antigen employed, appear in the blood. 



]\rany attempts have been made to determine experimentally 

 where the antibodies are produced. One of the most successful 

 methods of investigation has involved an attempted blockade of the 

 cells of tlic rcticulo-endothelial system by injecting inert particu- 

 late matter such as India ink. Au excellent review of the subject 

 is given by Howell (1928). She concludes that while the evidence 

 points to the reticulo-endothelial system as tlie source of anti- 

 bodies, the question is not definitely settled. 



Since the publication of Howell's ])aper Cannon, Baer, Sullivan, 

 Webster (1929), Kroo and Jancs(3 (1931) have published results 

 that quite definitely implicate the reticulo-endothelial system as an 

 important source of hemolysin and perhaps other antibodies. 

 Cannon et al. give a critical review of previous work and point out 

 many sources of error. They find that the manner of administra- 

 tion and the amount of antigen injected affects the liberation of 

 hemolysin following blockade. They also determined that an in- 

 complete blockade increases the amount of hemolysin production 

 while a complete blockade inhibits antibody production. Their 

 work is carefully controlled and apparently supports the theory 

 that antibodies are produced by the reticulo-endothelial system. 

 Plate III shows fixed phagocytic cells in various tissues. They 

 have taken up India ink injected intravenously to produce a ])lock- 

 ade of the reticulo-endothelial system. 



11. The cells of the reticulo-endothelial system form the main 

 defense mechanism of the body against infectious agents after the 

 latter have once gained entrance. This is discussed more ex- 

 tensively in Chapter VII. Bunting (1938) says that there is sug- 

 gestive evidence that they may aid in preventing invasion of the 

 body. 



