Flow cytometry of MIP-101 and CX-1 human colorectal carcinoma cells. MIP-101 (2 × 10³) or CX-1 (2 × 10⁵ ) were treated with murine anti-Fas antibody and then stained with fluorescein-conjugated antimouse antibody as described in the Materials and Methods. MIP-101 (MIP-101) cells display greater fluorescence (mean channel, 512.76) than CX-1 (CX-1) cells (mean channel, 5.73), indicating greater expression of Fas antigen on the latter cell line.