H. GIDEON WELLS 70Q 



from one animal exhibits immunological specificity which distinguishes it from the 

 corresponding proteins of the blood of any other species of animal, as well as the 

 specificity that distinguishes it from the other proteins of its own species, it is apparent 

 that a single protein may exhibit more than one sort of specificity. In hen eggs five 

 different proteins have been separated by chemical means, and these are immuno- 

 logically distinct from one another. Seeds often show numerous distinguishable 

 proteins in the same species. 



On the other hand, a common antigen may occur in many and cjuite unrelated 

 species. Such common antigens are particularly likely to be proteins that serve only 

 for purposes of structure or food, since they do not need to be specific as are the pro- 

 teins entering more actively into life-processes. So we find casein and ovalbumin 

 lacking species specificity, likewise some plant-seed proteins.' Lens proteins are im- 

 munologically related in many if not all species, although so foreign to the blood of 

 their own species that an animal can be sensitized against its own crystalline lens. 

 In the case of the so-called "heterogenetic" antibodies of Forssman,^ the hemolysin 

 antigen effect seems to depend on lipoid radicals common to different species, at- 

 tached to antigenic proteins which of themselves lack this particular property of 

 inciting hemolysin formation.^ 



BASIS or SPECIFICITY 



This seems to lie in specific chemical differences in the antigenic proteins, for it 

 has been repeatedly shown that immunological similarity of proteins is associated 

 with chemical similarity, and immunological differences are associated with chemical 

 differences. 4 For example, the readily isolated proteins of seeds have in many cases 

 been found to be chemically similar although from different seeds, and in this event 

 immunological tests have shown them to be closely related. On the other hand, two 

 chemically distinct proteins from the same seed have been found repeatedly to be 

 immunologically dissimilar. Thus, the crystallizable globulins from the seeds of 

 cantaloupe and squash are chemically, crystallographically, and immunologically 

 identical, 5 whereas globulin and proteose from scjuash seeds are chemically dissimilar 

 and immunologically unrelated to one another, despite the fact that both come from 

 the same seed. Or, to pass over to animal proteins, casein from the milk of any species 

 shows a closer biological relation to the casein of any other species than it does to 

 the whey proteins of its own milk, and the same is true of its chemical relations. Only 

 when very particular chemical methods are used can a difference be found in the 

 albumins of hen and duck eggs, consisting apparently in a different arrangement of 

 the same amino acids in the two albumins. This agrees nicely with the fact that al- 

 though by ordinary immunological tests these two albumins seem to be identical, 

 by delicate cjuantitative methods slight immunological differences can be discerned.'' 



' See Wells, H. G., Lewis, J. H., and Jones, D. B.: /. Infect. Dis., 40, 326. 1927. 

 = Namely, tissue constituents found in most varied species which, injected into rabliits, engender 

 hemolysins for sheep corpuscles. 



■* See Doerr, R., and Hallauer, C: Ztschr.f. Iinmiinitatsforsch. 11. ex per. Tlicrap., 47, 291. 1926. 



■• See Wells, H. G.: J . Inimioiol., 9, 291. 1924. 



5 Jones, D. B., and GersdorfT, C. E. F.: /. Biol. Chem., 56, 79. 1923. 



'Dakin, H. D., and Dale, H. H.: Biochem. J., 13, 248. 1919. 



