COMPOUND PROTEINS 155 



a compound protein should represent a new antigen giving rise 

 to antibodies for itself as distinguished from the antibodies for 

 its constituents. Unfortunately a formidable technical difficulty 

 stands in the way of clearly recognizing the presence of anti- 

 bodies which are specific for the compound protein. This is the 

 difficulty which is constituted by the fact that any protein which 

 is capable of being split by hydrolysis into moieties which are 

 still proteins (in the sense that they are antigenic) gives rise on 

 injection into animals to antibodies^ not only for itself, but also 

 for these split-products (31). Analogously, a compound protein 

 gives rise to antibodies for its constituent parts and it is only 

 possible to distinguish between these, which would appear in 

 the blood of immunized animals after injection of the separate 

 constituents, and any antibodies which may be formed for the 

 compound as a whole in those doubtless exceptional instances 

 in which the antibody for the compound reacts with a constituent 

 which is not normally antigenic. 



We have therefore investigated from this point of view certain 

 compound proteins in which one constituent is non-antigenic, 

 such as protamin caseinate, of which the protamin constituent 

 is non-antigenic and toxic while the casein constituent is anti- 

 genic and non-toxic, and globin caseinate of which the globin 

 constituent is toxic and non-antigenic.* 



Protamin caseinate displays no antigenic characteristics which 

 enable it to be distinguished from casein. It is non-toxic, but 

 whether this lack of toxicity is attributable to the masking of 

 the toxic properties of protamin by its combination with casein, 

 or to the smallness of the proportion of protamin contained in 

 the compound has not yet been definitely established. It gives 

 rise to antibodies for casein by virtue of its casein-content, just as 

 casein gives rise to antibodies for its split-product paranuclein, but 

 it does not give rise to antibodies for protamin. Similarly, pro- 

 tamin edestinate (111) is non-toxic and gives rise to antibodies 

 for edestin but does not give rise to any antibody which will 

 react with its protamin constituent. Globin caseinate, however, 



* It is asserted by C. H. Browning and G. H. Wilson (23) that globin is 

 antigenic. The negative results of Gay and Robertson which have been 

 repeated and confirmed by Schmidt show that the antigenic character of the 

 globin prepared by Browning and Wilson must have been due to contamination 

 by protein impurities. 



