Abstract
The authors 1 have previously examined, from an arithmetical point of view, the Buchnerian hypothesis that antibody is a conjugate of body globulin and injected antigen. These speculations led us to undertake the following experimental investigation based upon the reactivity of artificial compound proteins in which the hapten chosen to confer the new specificity contains integrally an inorganic atom (As) for which a direct and very delicate chemical test is available. Two compounds, ovomucoid-diazo-arsanilic acid and casein-diazo-arsanilic acid, were prepared. The serum of a rabbit immunized against the first reacted with the second, showing the presence of an arsanilic-aeid-specific antibody. The optimal precipitation ratio by volumes of antiserum to casein-diazo-arsanilic acid was found to be about 150. Such a mixture is considered neutral— at least neither reagent is present in any large excess. It seems reasonable to suppose that within this zone, antibody and antigen enter respectively into the precipitate in the proportion of one molecule to one molecule, or one molecule to a small number of molecules. If it is assumed that the antibody is a globulin conjugate of the antigen, and contains a similar amount of arsenic (as would necessarily be true if there were no breaking up of the injected antigen), it can be shown from the amounts of arsenic and casein found in the casein-diazo-arsanilic acid solution, and the above ratio, that 10 cc. of antiserum should have contained about 20 mmg. (20 × 10-6 g.) of arsenic, an amount easily detectable. None was found. This would seem to cast doubt on the Buchnerian hypothesis.
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