Purified anti-FCRL1 immunotoxins and their binding abilities. (A) Purified E3(Fv)-PE38 and E9(Fv)-PE38 on SDS-PAGE. (B) Binding of 60 nM E3(Fv)-PE38 and E9(Fv)-PE38 to Ramos cells. SS1P, an antimesothelin immunotoxin, was used as negative control. (C) Apparent affinities of E3(Fv)-PE38 and E9(Fv)-PE38 on Ramos cells. Binding saturation curve and nonlinear re-gression analysis were conducted with GraphPad Prism (GraphPad Software, San Diego, CA).