Effect of the addition of rmSCF on the expression of 4 protein on the surface of +/+, mi/mi, orW/W^v CMCs. Three weeks after initiation of the culture, various CMCs were incubated with 10% PWM-SCM and 50 ng/mL rmSCF for 0, 1, or 2 weeks. The surface expression of integrin 4 subunit was examined by flow cytometry. Cells were incubated with either rat anti-4 MoAb (solid line) or control rat IgG (dotted line).