54 COLLECTED STUDIES IN IMMUNITY. 



two sera and the mixture centrifuged some time after, it will be 

 found that the milk immune body has been completely abstracted 

 from the serum, but the blood immune body only partially so. Cili- 

 ated epithelium, therefore, combines more strongly with the milk 

 immune body than with the blood immune body. 



On the other hand, the blood immune body possesses a greater 

 affinity to the erythrocytes than does the milk immune body. Thus 

 if equal amounts of cattle blood are added to the two inactivated 

 immune sera (amounts which would be completely dissolved if suf- 

 ficient complement were present), it will be found after a certain time 

 that the blood immune body has been completely bound by the 

 red blood-cells, whereas the milk immune body can still partially be 

 demonstrated in the serum. 



If one tests a number of different cow milk immune sera in this 

 way, the results will show marked variations. My experiments were 

 conducted on four different cow milk immune bodies which had 

 been obtained by injecting rabbits with cow milk. Three of these 

 showed considerably less affinity to the red blood-cells than did 

 the specific blood immune body obtained by treatment with blood. 

 The fourth, however, was bound by the red blood-cells in about the 

 same degree as was the blood immune body. On the other hand, 

 cases were observed in which the serum of rabbits after these had 

 been injected with cow milk showed only a very slight hscmolytic 

 action, and this only on the most sensitive of the blood-cells. 



All of these differences manifested themselves quite independ- 

 ently of the cattle blood employed in the experiment and must there- 

 fore be ascribed to differences in the immune sera themselves. Pos- 

 sibly they are due to variations in the kind of receptors, such as 

 were found in a marked degree in the experiments of Ehrlich and 

 Morgenroth on isolysins. 1 The strong affinity of the hsemolytic 

 milk immune body for tracheal epithelium, however, was present 

 in all the cases examined and it did not differ materially from the 

 chemical relationship between ciliated epithelium and its specific 

 ciliated epithel immune body. 



Hence by treatment with cow milk we obtain a haemolytic immune 

 serum which differs from the blood immune serum, but cannot with 

 certainty be differentiated from the ciliated epithel immune serum. 



1 See page 23. 



