Immunostaining of formalin-fixed, paraffin embedded human tonsil section with rat anti-λ-light chain using diaminobenzidine as chromogen (dilution 1 : 5000, brown) and biotinylated mouse anti-κ-light chain using RED AP as chromogen (cat. no. HS-346 011BT dilution 1 : 2000; red). Nuclei have been counterstained with haematoxylin (blue).