Binding characteristics of hL243γ4P and hL243γ1 relative to the parental murine L243. (A) Binding of hL243γ1 to Raji cells was measured using PE-conjugated second antibody (goat anti-human IgG, Fc fragment specific) and counting in a Guava PCA system. (B) Competitive binding assay. A cell-surface competitive binding assay was performed to compare the binding activity of hL243γ4P with the parental murine L243. Varying concentrations of mL243 (▪) or hL243γ4P (▴) were mixed with a constant amount of ¹²⁵I-hL243γ4P and incubated with Raji (left) or Daudi cells (right). The cells were washed to remove unbound mAbs and counted for the bound residual radioactivity. (C) Direct cell-surface saturation binding and Scatchard plot analysis on Daudi cells. mL243, ▪; hL243γ4P, ▴.