The measurement of the combining power of diphtheria toxin and toxoid with anti-toxin in relation to their antigenic efficacy / by A.T. Glenny, C.G. Pope, and Hilda Waddington.

Glenny, A. T.

Date:: [1925?]

Credit: The measurement of the combining power of diphtheria toxin and toxoid with anti-toxin in relation to their antigenic efficacy / by A.T. Glenny, C.G. Pope, and Hilda Waddington. Source: Wellcome Collection.

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$(Glenny and Allen 1921, Hartley and Hartley 1922). Such a mixture contains 1 M.E.D. of toxin uncombined. If the mixture were not diluted to the Lr/500 level but contained 1 unit of antitoxin in place of l/500th there would be 500 M.E.D.s free. We have found with the few toxins we have tested that the minimal oedema dose is about l/20th of an M.L.D. while approximately l/50th of an L+ mixture will just produce oedema: it is difficult to determine these values with accuracy but these ratios appear approximately correct. If as we believe a single body, toxin, causes both oedema and death, then oedema is produced by a definite fraction of an M.L.D., and because there is just 1 M.L.D. of toxin free in an L+ mixture, this same fraction of an L+ mixture should just cause oedema. But these fractions are not identical, for the different ratios mentioned above are well outside experimental error. We suggest that when a fraction of an L+ mixture between 1/20 and 1/50 is injected, sufficient toxin may become dissociated to produce oedema. Thus the various units of measurement depend for their estimation not upon fixed amounts of toxin being left free but upon the amount of toxin which is free or becomes free from a toxin antitoxin combination ^ and is then absorbed. In the following argument we have assumed ? the amount of toxin absorbed and the amount left uncombined to be sufficiently near that the difference can be ignored. The Lo dose is not always defined as above. According to , Ehrlich (1903) ‘Hhe Lo dose of a toxin is that amount of poison i which is completely neutralised by one immune unit ” and further, in i the Lo mixture “all the constituents of the poison are completely ; neutralised so that not only the single amount but also high [ multiples of this can be injected into guinea-pigs without causing j a trace of a local or general reaction.” The Lo dose as usually determined is that amount of toxin which when mixed with 1 unit i of antitoxin and injected fails to produce a reaction. In practice we r find that “ high multiples ” of such a mixture may produce oedema sj and even death. It follows that the neutralising value assigned to a toxin depends 1 to a certain extent upon the sensitiveness of the test applied; the i most sensitive test for detecting traces of unneutralised toxin con- sists in injecting 5 c.c. or more of the mixture subcutaneously into ! guinea-pigs. With a toxin of average strength the intracutaneous I injection of 0'2 c.c. of the mixture is almost as sensitive a test and I more sensitive than that of a single Lo dose mixed with 1 unit of i antitoxin. It follows that the Lr value of a toxin determined i intracutaneously records a higher strength (i.e. a smaller volume for i the unit) for the toxin than the Lo value determined subcutaneously, ! unless the latter value has been obtained by injecting “high multiples”; of the mixture. When Lr/500 titrations are made, the mixtures arei diluted so that only l/500th of the normal quantities are injected;^$