FURTHER STUDIES ON THE IDENTITY OF PRECIPITINS AND PROTEIN SENSITIZERS (ALBUMINOLYSINS).

The experiments here recorded, as well as those preceding them and outlined in the introductory paragraphs, have had the purpose of analyzing the phenomenon of alexin fixation occurring when dissolved, unformed proteins are added to their specific antisera. The present experiments have shown that specific precipitates have the same relation to the complement fractions first described by Ferrata that are possessed by sensitized cells. In this they differ from indifferent suspensions, like kaolin, which fix alexin and its fractions indiscriminately, fixing the end-piece without dependence upon previous adsorption of the mid-piece. The writer believes this to be of theoretical importance since it seems to show, in the first place, that the fixation of alexin by precipitates is not merely a mechanical adsorption, and in that it renders more likely the supposition that the so called precipitin is actually a protein sensitizer by which a foreign protein is rendered amenable to the proteolytic action of the alexin. The visible precipitation in such reactions is merely secondary, occurring because of the colloidal nature of the reacting bodies, under conditions of quantitative proportions and environment which favor flocculation. It does not seem necessary to assume a structure for the so called precipitins essentially different from that of other sensitizers. Carried to its logical consequences, the acceptance of this view, taking the identity of agglutinins and precipitins at least as a possibility, leads to the conception that functionally there is but one variety of specific antibodies, and that is the sensitizer which makes possible the action of alexin or complement upon various antigens.