Fluorometric estimation of antigens (antibodies).

A method for the titration of antigens based on separation by filtration through millipore filters of the complex of antigen with fluorescein isothiocyanate-labeled antibodies from free labeled anti­ bodies and nonspecific y-globulins is described. The fluorescence of the antigen-antibody complex is measured directly on the millipore filters using the Turner fluorometer equipped with a paper chromatogram door. The limit of sensitivity of the method is about 0.05 fig of antigen protein. Quenching of fluorescence by nonlabeled antibodies can be used for the titration of antisera. An example of the application of the method for titration of rabies virus antigen is also presented.