The abscissa represents the mean fluorescence intensity of the cells analyzed from the animals on day -7 (before MoAb administration), and on day 0 (day of transplant) of an animal that received MoAb S5. Cells were stained with either goat antimouse FITC (to detect surface MoAb) or S5-FITC, which is the direct FITC conjugate of MoAb S5. Cells removed from the animal on day 0 had surface MoAb, as shown by staining with goat antimouse FITC, although not saturation levels, as additional MoAb S5 binds to cells (S5-FITC).