The chemical aspects of immunity / [Harry Gideon Wells].

  • Wells, H. Gideon (Harry Gideon), 1875-1943.
Date:
1929
Catalogue details

Licence: In copyright

Credit: The chemical aspects of immunity / [Harry Gideon Wells]. Source: Wellcome Collection.

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    facts. Furthermore, kober 108 was unable to secure spectroscopic evi- dence of the keto-enol tautomerism suggested by Dakin as the explana- tion of racemization, and advances theoretical reasons indicating that the proteins cannot have as many free terminal amino and carboxyl radicals as Dakin's hypothesis requires, for this makes the assumption that all the active amino acids obtained by hydrolysis of racemized proteins must have occupied terminal positions in peptid linkages. F. C. Koch has pointed out to me, however, that Kober’s criticism of Dakin’s hypothesis is not conclusive, because it is by no means certain, and even doubtful, that at every peptid linkage it has gone through the enol stage. Bacterial Toxins In considering whether anything except intact or nearly intact pro- tein molecules can function as antigens, we meet at once an important problem in the bacterial toxins. These substances are characterized by their antigenic capacity, and yet it is not known whether they are pro- teins or not. Although they behave like colloids they diffuse more rapidly than proteins usually do, and very active toxins have been pre- pared that do not give the ordinary reactions for proteins. This last, of course, may merely mean that the toxins are so powerful that they are active in solutions so dilute that they do not respond to these tests. As an illustration of this possibility we have the case of ricin, the poisonous antigenic toxin of the castor oil bean. This has been isolated 108 in such purity that one-one thousandth of a milligram (0.000,001 gram) is a fatal dose per kilo of rabbit, and smaller than lethal doses lead to antibody formation, i.e., are antigenic. Nevertheless, ricin is inseparably associated with, and apparently iden- tical with, the coagulable albumin of the castor bean. Because of the minuteness of the lethal dose some observers had thought that this vegetable toxin was not a protein, for they had obtained active solutions giving no protein reactions. Toxins do not owe their antigenic effect solely to their toxicity, since when detoxicated with formalin or some other agents they retain their antigenic activity,110 thus resembling proteins which also are antigenic whether toxic or not. Conversion into non-toxic “toxoids” 111 by formalin, iodin, or carbon disulfide is non-reversible but detoxifica- tion by soaps is reversible. When toxins are detoxicated with acids 108 ]. Biol. Cliem., 22:433 (1915). 100 Osborne, Mendel and Harris, Am. J. Physiol., 14:259 (1905). 110 Ramon, Ann. Inst. Pasteur 39:1 (1925). 111 See review on toxoids by Bacher, Z. Immunitdt., 54:21 (1927).