A, Lack of Fab m912 binding to mesothelin-negative (A431) cells. B, Binding of Fab m912 but not of a control Fab to mesothelin-positive H9 cells. C, Binding of scFv m912 but not of a control scFv to mesothelin-positive H9 cells. In all three panels, thick lines represent binding of m912 in Fab or scFv formats and thin lines are for control Fab and scFv. The concentrations of all Fabs and scFv are 40 nM and 100 nM, respectively.