Phenotype of XG-1 tumors in SCID mice. The tumors growing in SCID mice grafted with XG-1 cells and injected with agonist anti-gp130 MoAbs were harvested and put in suspension. Viable cells were recovered by centrifugation on a Ficoll-hypaque density medium and cells were labeled with MoAbs to various antigens or control murine antibodies. Fluorescence was analyzed with a FACSCAN apparatus. The dashed line represents the fluorescence profile with a control antibody and the solid line is with MoAbs to specific antigens. The percentages of cells labeled with the different MoAbs are indicated in the panels.