Immunohistochemical detection of H22xKi-4 in a lymph node biopsy after treatment.

For the immunohistochemical investigation, the tissue was deparaffinized, cut into sections of 5 μm, and blocked with pig serum for 10 minutes to reduce unspecific staining. To detect the murine part of the bispecific molecule (Ki-4 F(ab′)), a polyclonal rabbit antimouse Ab was applied and incubated at 4°C overnight, followed by a biotylinated pig antirabbit antibody and a standard biotin-streptavidin kit. Finally, the slides were stained with fast red. There is clear staining of the H-RS cells. The numerous small lymphocytes in the specimen are negative. The biopsy of a second patient showed an identical staining pattern.