Note that only a small proportion of tumor cells are immunoreactive. Bouin's fixative must be used. Some investigators have shown apparent immunoreactivity in the cytoplasm only with formalin fixation. For some of these, these results may represent nonspecific staining.
Proper controls can help differentiate between specific and nonspecific staining.
Right - ras p21 on rat bladder tumor cells, Bouin's fixative. CD3 is found in many species and paraffin sections can be used with fixatives other than formalin. Middle - B220 in B cell zones of mouse spleen, paraformaldehyde fixation, biotinylated mouse monoclonal antibody. This antibody will also immunoreact with formalin fixed tissues after microwave pretreatment. Left - HIV p24 in cytoplasm and on cell membranes of syncytial and other cells in vitro, formalin fixation.