Ascoli-Valenti Reaction

Ascoli-Valenti Reaction (Ascoli, Valenti). Bail, Gruber and Futaki made the observation that some anthrax antisera, when mixed with extracts from anthrax cultures or with abdominal effusion or edema fluid from animals that died of anthrax, cause protein precipitation. Ascoli and Valenti applied these precipitating properties of anthrax antisera with great success for the practical diagnosis of anthrax in dead animals and developed a special thermoprecipitation method for examining suspicious materials. They established that with highly active antisera, precipitates are obtained especially clearly, even with extracts from anthrax organs obtained by boiling. According to Ascoli and Valenti, boiling has the advantage that due to the rapid coagulation of protein, a completely transparent extract is obtained. The thermoprecipitation method, or A.-V. reaction, gives a positive result even in cases where the anthrax material has been undergoing decomposition or drying for months or even years. Preservation of organs or tissues of dead animals with chloroform, alcohol, glycerin, or formalin does not prevent the reaction from occurring if these materials are washed from the preservative substances before examination. The A.-V. reaction is particularly demonstrative when active antiserum is layered with extract from anthrax material. After a few minutes or even a few seconds, protein precipitation appears in the form of a gray-white disk or ring at the boundary where the two liquids meet, which is especially clearly visible when examining the tubes against a dark background; over time, this precipitation ring continues to increase. The essence of the A.-V. method is based on the fact that anthrax bacilli, like other microbes, consist of specific protein substances; the latter are precipitogens. When they are injected into animals parenterally, precipitins are formed in the blood of the latter. According to Januschke, in the thermal reaction, neither dissolution nor leaching of anthrax capsules, bacilli, or spores takes place; only the protein from previously disintegrated anthrax bacteria becomes apparent. In a living patient, the A.-V. reaction can be positive only if bacteremia occurs: only with progressive increase in the disintegration of bacilli (anthrax) in the living or dead organism does the precipitating power increase. The most difficult part of the A.-V. reaction is the preparation of highly active precipitating serum. Ascoli recommends obtaining it from donkeys and horses. In Russia, such a serum was prepared by S. A. Alekseev, N. A. Pokhishevsky, D. A. Radkevich, and others. Rosenberg and Romanov propose, for immunizing horses, sheep, rabbits, in order to obtain highly titered and strictly specific precipitating anthrax antiserum, to prepare the antigen by a somewhat modified method of Fujiwara. After 1¹/2 months of immunization by Romanov, a highly active precipitating serum with a titer of 1:100,000 was obtained.

Mehn. (from Greek meion - less and stagma - drop), proposed by Ascoli and Izar as a biological method for recognizing cancer. The reaction is based on the reduction of surface tension of the patient's serum diluted with physiological NaCl solution, mixed with antigen. The latter represents an alcohol-ether extract from malignant tumors, but it can also be prepared from some normal organs. Surface tension is measured by counting drops using a stalagmometer. Compared with control normal serum, cancerous serum gives a significant increase in the number of drops. The diagnostic value of the reaction has not yet been clarified.