Abstract
Complement is fixable by various substances. It is fixed by different extracts containing certain proteins. Fixation in this case is direct and non-specific. On the other hand, complement is also fixed by a combination of specific antigens and antibodies (Bordet-Gengou). In the last instance, fixation is accomplished by the coöperation of the antigen and antibodies, the latter being inert without the aid of each other. From this observation the deduction was formed that whenever complement is fixed by a mixture of two substances, it is an expression of a specific reaction taking place in such a mixture. This assumption, however, is permissible only when the above phenomenon can be produced by none but the specific antigens and antibodies.
Recently I encountered a peculiar phenomenon which resembles very closely the true Bordet-Gengou reactions, differing from the latter in the non-specific nature of the substances serving as antigen. Working on the sera of tuberculous patients, using tuberculin and the nucleoprotein of tubercle bacilli as antigen, I found that twenty out of twenty-five cases gave complement fixation in varying degrees when tested in unheated state. Encouraged by this result, I examined thirty-five control cases without tuberculosis and found, to my surprise, that twenty-eight of these gave positive reactions with the same antigen.
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