Western blotting: remembrance of things past.

Western blotting sprung from the need to develop a sensitive visual assay for the antigen specificity of monoclonal antibodies. The technique employed SDS-PAGE of protein antigens, electrophoretic replica transfer of gel-resolved proteins to unmodified nitrocellulose sheets, probing the immobilized antigens with hybridomas, and detection of antibody-antigen complexes with radiolabeled staphylococcal protein A and autoradiography. The simplicity and relevance of the method have led to its expansive application as an immunodiagnostic and a ubiquitous research tool in biology and medicine.