A simple method of detecting the circulation of antigen in the blood. (Preliminary note.)

Abstract

Experience with different immunity reactions has brought in the last few years a realization of very important limitations of their usefulness. It is generally conceded that it is impossible by means of immunity reactions to differentiate between actual infection and the state of immunity following it. This difficulty was especially brought out in the beginning of the present war, when it became necessary to differentiate between the soldiers who gave positive Widal reactions due to previous prophylactic vaccinations, and those actually infected, or those who may be carriers. It was suggested by German authors that the complement deviation test may solve this problem in so much as, in their experience, artificial immunization by means of a vaccine, although followed by the development of agglutinins, did not seem to influence the production of the complement-fixing antibody in any marked degree. This suggestion was followed up in many laboratories abroad as well as in this country. In our own laboratory, for instance, this question was studied during the last two years by Doctors G. C. Simpson and J. R. Johnston, but the conclusions drawn were not very encouraging. The necessity of differentiating between actual disease and the state of immunity is not limited to the case of typhoid. Since it has become the practice in large institutions to apply the Shick test, it has also become necessary to differentiate between individuals containing antitoxin in their blood as a result of natural immunity and those who may be harboring a mild infection or those who may be carriers. In case of diagnosis of gonnorhea many workers have noticed that often very old cases without any symptoms of the old infection for many years, still frequently give a positive complement deviation test.