Efficient immunostaining of tissue sections with chemically modified monoclonal antibody.

Monoclonal antibodies (mAbs) were modified with a photo-cross linker, sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1,3'-dithiopropionate (SAND), and their efficacy in immunohistochemical staining of tissue sections was examined comparatively with that of unmodified mAbs. mAbs used were HBJ127 and SV2-61 gamma which recognized a proliferation-associated human gp125 cell surface antigen and a human c-erbB-2 protooncogene product, respectively. Both mAbs could stain relevant cancer tissue in frozen sections but not that in paraffin sections. Whereas SAND-modified mAbs intensely stained the cancer tissue in paraffin sections too, and the UV irradiation to SAND-modified mAb-treated tissue sections further increased the intensity of the staining. Scatchard plot analysis using 125I-labeled mAbs indicated that the augmentation of staining capacity by the SAND modification is due to the increase of the mAb amount capable of binding to the antigen.