A solid-phase immunofluorescence assay (SIFA) for screening antigen-specific hybridomas

A solid-phase immunofluorescence assay (SIFA) is described for screening of monoclonal hybridoma antibodies against soluble antigens. The test is simple, needs a small amount of material (20-100 ng of labeled antigen per sample) and allows a large number of samples (500-1 000) to be tested in 2 days. The assay is performed in microtitration plates with small cellulose nitrate discs as the solid phase. Anti-mouse IgG, the sample to be tested and FITC-labeled antigen are successively incubated with the discs. The fluorescence intensity of the surface of the discs is then measured with a microfluorometer. The assay has been used to select hybridomas against human serum albumin. Comparison of the immunofluorescence assay with a radioimmunoassay using conventional antisera and hybridoma antibodies similar sensitivity for both assays.