The chemical aspects of immunity / by H. Gideon Wells.

  • Wells, H. Gideon (Harry Gideon), 1875-1943.
Date:
1925
Catalogue details

Licence: In copyright

Credit: The chemical aspects of immunity / by H. Gideon Wells. Source: Wellcome Collection.

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    the change resulting in precipitation. When the latter group is destroyed hy heating to 720, the precipitin is converted into a precipitoid, which possesses the property of preventing the precipitation of unheated pre- cipitin hy the specific antigen. Bacterial precipitinogens are relatively resistant to moderate heating, and heated extracts of bacteria are used for precipitin tests under the name thermoprecipitins.80 The Character of the Precipitate It was first assumed that the precipitate was composed of the antigenic protein converted into an insoluble modification by the action of the precipitin, and the early literature referred to the antigen as the “pre- cipitable substance,” but it has been shown that the precipitate originates chiefly in the proteins of the immune serum, especially by the work of Moll81 and of Welsh and Chapman.82 As the precipitate is said to be able to sensitize anaphylactically, both actively and passively, it would seem that it must contain both the antibody (which confers passive sen- sitization) and antigen (to cause active sensitization) (Weil).83 The discrepancy between the amount of antigen and the amount of precipitate may be very great; for example, in one experiment of Welsh and Chapman, when 1 mg. of egg albumin reacted with a specific antiserum the precipitate weighed 25.9 mg. Just how much of the antigen is present in such precipitates does not seem to have been determined. As stated above, Weil found enough to sensitize guinea pigs to the antigen, and specific precipitins for both the antigen and the antibody were obtained by Fujiwara84 on immunizing with the precipi- tate; but Doerr and Moldovan85 and Chickering80 failed in similar experiments, which contradictory results indicate that there is so little antigen present that it may be merely admixed with the precipitate and not actually a part of the reaction product, or else so altered that it is no longer antigenic.87 The precipitate may, when of maximum amount, contain more nitro- gen than corresponds to the entire euglobulin of the immune serum, and the euglobulin apparently contains all the precipitin, so it seems prob- able that the precipitate consists of more tjian the precipitin alone; it may be added that the precipitate is always less in amount than the total globulin of the antiserum.88 The amount of precipitate is always greater when the reaction is between homologous antiserum and antigen, than with even closely related but heterologous antigens,80 so that the quantitative measurement of the precipitate is of value in applying this reaction to determine the nature of protein solutions. The dilution of