FIG. 2.

Human breast carcinomas coexpress FasR and FasL. Immunoperoxidase staining with a FasR-specific rabbit polyclonal IgG antibody (FasR Ab) was performed with paraffin-embedded breast carcinoma sections. A consecutive section from each tumor was used for immunohistochemical detection of FasL with a FasL-specific rabbit polyclonal IgG antibody (FasL Ab). Slides were counterstained with hematoxylin. FasR-positive immunohistochemical staining (brown) is shown in a representative breast carcinoma (magnification, ×100). The same tumor region is also positive for FasL expression, indicating coexpression of FasR and FasL by breast tumor cells in vivo. As a control for specificity of antibody detection, the appropriate immunizing peptide (FasR or FasL) was included during primary antibody incubation. Competitive displacement of staining by the soluble peptide immunogen confirmed the specificity of FasL detection (Fig. 1) and FasR detection (data not shown). These results are representative of 17 breast carcinomas.