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.

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    filter candles used or other obscure causes, and different bottles may deteriorate at different rates. In order to detect such differences we test each bottle after filtration and immediately before use for immunisation, and the last remains of toxin in each bottle are tested to detect possible deterioration during use. In a series of 127 bottles representing 14 blended batches of toxin only 4 gave a value more than 10 per cent, different from the average value for each batch. When accurate results are needed flocculation must be delayed. Curves 1, 9 and 10 on chart 1 show the relation between the time of flocculation and composition of mixtures containing one toxin (T.a.) and three different antitoxins (AT.l., AT.3. and AT.4.). The minimum flocculating times are 6, 30 and 122 minutes respectively. The accuracy to which a toxin can be titrated depends mainly upon two conditions (i) the ease with which the first mixture to flocculate can be chosen from adjacent mixtures, (ii) the extent to which uncontrolled conditions may so accelerate or retard flocculation in one tube or another that the flocculating time of the balanced mixture is delayed beyond that of other mixtures. Uncontrolled conditions such as unequal rates of heating in different tubes may delay flocculation for several minutes ; it is obvious that such a delay is of less significance in a series of slowly flocculating mixtures than in a series of fast ones. For the purposes of comparison we have chosen as an index of possible accuracy the extreme range of antitoxic content of all mixtures floccu¬ lating within 5 minutes of the first tube to flocculate. Thus from curve 1 it is seen that all mixtures containing between 16'6 and 24'0 units of antitoxin AT.l. per c.c. of toxin T.a. flocculate within 6 to 11 minutes of mixing. When another serum AT.3. is used the first mixture flocculates in 30 minutes and within the next 5 minutes all mixtures containing between 18-7 and 23’0 units per c.c. of toxin have flocculated. Closer limits are obtained with a still slower serum; AT.4.; the first mixture flocculates in 122 minutes and only those mixtures containing between 20-5 and 22'0 units of antitoxin flocculate: within the next 5 minutes. Thus it is seen that more accurate but: slower results can be obtained by using such a serum as AT.4. mi preference to AT.l. It must be pointed out, however, that the: rapidity with which flocculation occurs in mixtures other than the: balanced mixture is not simply a function of the minimum time o: flocculation. With certain sera flocculation may occur almosj simultaneously in a number of tubes. The increased accuracy of testing when mixtures are kept at lowe:: temperatures is shown graphically on curves 2, 11 and 12 on chart 1 showing the relation between time of flocculation and composition o mixtures of another toxin T.b. with antitoxin AT.l. when the mixture, are kept at 50°, 35° and 25° C. The times of flocculation at the differem temperatures were 15, 29 and 56 minutes, and the antitoxic content oi mixtures flocculating within 5 minutes were 9-7 to 13‘6, 10'7 to 13*q
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