Quantitative specific antigen determination using fluorescent antibody 1

In the process of a study of multiplicity reactivation with T2 bacteriophages in our laboratory, a sensitive assay for T2 coat protein in the presence of other proteins was considered to be desirable. The technique which was developed to accomplish this was first applied to the simple infection of Escherichia coli B by T2r+ bacteriophages. The description of this technique and the results of this particular experiment form the body of this report. The application of the technique to multiplicity reactivation studies will be reported separately in connexion with other reactivation experiments. The detection of antigen by immunofluorescent techniques has been widely employed for the localization in tissue and cells of specific antigens. This has been particularly pronounced since the work of Coons and Kaplan (1950). Because of the relative specificity of this qualitative method, it was considered as a basis for the development of a simple quantitative technique for specific protein assay even in the presence of other antigenic materials including other proteins. In addition, fluorescent materials may be detected in low concentrations by means of readily available instruments for spectrofluorometry. The quantitative precipitin technique is well known as an analytical method for the estimation of antigen or antibody. With micro Kjeldahl methods for nitrogen determination, it has been shown that a linear relationship exists between antigen N precipitated and antigen added in the region of antibody excess. In the development of the technique reported here, under similar conditions, a linear relationship between the amount of fluoresc-