50 COLLECTED STUDIES IN IMMUNITY. 



This, of course, is readily understood by means of the side-chain 

 theory. One could not well assume that all the side-chains of a 

 certain group of cells are entirely different from all the side-chains 

 of the rest of the cells. It is much more probable that certain groups 

 which serve general functions of nutrition are common to the majority, 

 if not to all, of the cells of the same animal. 



When, therefore, after the injection of ciliated epithelial cells 

 we see a hsemolytic immune body develop, we may assume that 

 among the groups of the ciliated epithelial cell which effect the 

 immunity, there are some which are identical with those of the red 

 blood-cell or at least closely related to them chemically. 



If this view is correct we should expect that, conversely, the 

 immune body of an immune serum derived by treatment with blood, 

 would be bound by ciliated epithelial cells of the same species. The 

 facts correspond entirely with this assumption. According to my 

 experiments, epithelial cells from the trachea of cattle are able par- 

 tially to bind the blood immune body derived by treating rabbits 

 with cattle blood. The affinity of the ciliated epithelium for the 

 blood immune body is, however, as already mentioned, less than 

 that for the hsemolytic ciliated epithelial immune body of the rabbit 

 immune serum. 



With this a further fact of considerable importance becomes 

 manifest. Although the ciliated epithelial cells are destroyed by 

 the ciliated epithelial immune body (provided sufficient complement 

 is present), it has thus far been impossible to demonstrate any injury 

 of these cells resulting from the binding of the active blood immune 

 body. The epithelial cells thus differ from the red blood-cells, which 

 are destroyed even by the antiepithelial serum. We shall not enter 

 into an explanation of these phenomena, which point to a multiplicity 

 of antibodies produced in response to cell material. It will suffice 

 to point out that there is a whole series of substances which are 

 designated as blood poisons, because they attack especially the 

 red blood-cells while they have little or no effect on other cells. 



The fact that the blood immune body when supplied with com- 

 plement is bound by the ciliated epithelial cells of cattle without 

 causing any apparent injury, proves, at least, that the phenomenon 

 of toxic action in no way shows whether or not a toxin or toxin-con- 

 taining substance has been bound by the cells. The appearance of 

 toxic symptoms, to be sure, in the case of antitoxin-forming poisons, 

 is proof that the poison has been bound. An absence of toxic symp- 



