Binding of Pg 1 to 1-LN cells and immobilized TF.

(A) Increasing concentrations of ¹²⁵I-labeled Pg 1 were added to 1-LN cell monolayers (1 × 10⁵ cells/well). Molecules of ligand bound were calculated after subtraction of nonspecific binding measured in the presence of 50-fold excess of nonlabeled ligand, as described in “Materials and methods.” (B) Increasing concentrations of ¹²⁵I-labeled Pg 1 (●) or Pg 2 (○) were added in triplicate to TF-coated 96-well culture plates and were incubated at 22°C for 1 hour. Bound Pg was calculated as described in “Materials and methods.” (inset) SDS/10%-PAGE of purified 1-LN cell TF (2 μg) under reducing conditions. Lane 1, Coomassie Brilliant Blue R-250–stained gel. Lane 2, blot incubated with goat anti-human TF F(ab')₂ followed by reaction with a rabbit anti-goat alkaline phosphatase-conjugated F(ab')₂. Data represent means ± SD from experiments performed in triplicate.