The titration of diphtheria toxin by the flocculation method / A.T. Glenny and U. Wallace.

  • Glenny, A. T.
Date:
[1925?]
Catalogue details

Licence: In copyright

Credit: The titration of diphtheria toxin by the flocculation method / A.T. Glenny and U. Wallace. Source: Wellcome Collection.

    1/16
    Rh 57 <* Reprinted from The Journal of Pathology and Bacteriology, VoL XXVIII., 1925 EARY y>-| IT. 19261 /si / jy THEyTITRATION OF DIPHTHERIA TOXIN BY THE FLOCCULATION METHOD. A. T. Glenny and U. Wallace. From the Wellcome Physiological Research Laboratories, Beckenham. 'N the past few months we have examined several thousand samples f toxin and found that the method of Ramon (1922) applied to toxin ilration can be carried out by assistants with but little previous raining. The method is so simple that it appears advisable to place m record a detailed account of our technique, for as Glenny Pope and addington (1925) have shown, the strength of a toxin determined by the flocculation method is of more value to the immunologist than he various animal determinations. In this paper we deal only with the test as applied to the titration of toxin. In a previous paper Glenny and Okell (1924) suggested a new unit, the Lf value of a toxin, which they defined as the amount of toxin established by flocculation to be equivalent to 1 unit of antitoxin. We would now suggest the following as the most accurate definition:— An Lf dose of toxin is the amount of toxin per unit of a certain chosen antitoxin in the mixture that flocculates more rapidly, under the same conditions, than all other mixtures con¬ taining other amounts of the same toxin per unit of the sam,e antitoxin. In practice it is more convenient to keep the volume of toxin constant and to determine the number of Lf doses per c.c. of a toxin by finding the number of units of antitoxin per c.c. of toxin which gives the most rapidly flocculating (mixture. For general routine purposes, to a series of narrow tubes of uniform bore containing 1*0 c.c. of the toxin to be examined we add a graduated series of quantities of antitoxin. The addition to the series is completed as rapidly as possible. The toxin and antitoxin in each tube are mixed by inverting the tube, the contents being protected from the thumb by means of a piece of non- labsorbent paper about an inch square; a separate piece of paper is used for each tube. The tubes are immersed to a uniform depth in a water bath kept at about 50° C., and examined at suitable intervals until a fine precipitate appears in one tube; this precipitate rapidly becomes more pronounced and flocculates; precipitates soon appear in adjacent tubes. The use of the Trevan microsyringe enables small volumes of antitoxin to be measured accurately. The amount of the liquid delivered by the micro- Ssyringe is controlled by the distance the plunger is made to move; this is laccurately gauged by means of a micrometer head. By careful selection, syringes may be chosen that will deliver O'l c.c. for a given number of turns. Still further choice can link the syringe with the strength of the standard 317 A I ■