(A) Detection of TIE and TEK proteins in transfectants. Cell lysates were obtained from BaF/vector (lanes 1 and 5), BaF/TIE (lane 2), and BaF/TEK (lane 6) cells that were surface-biotinylated. Proteins in lysates were immunoprecipitated with anti-TIE (lanes 1 and 2) or TEK (lanes 5 and 6) MoAb. Immunoprecipitates were separated by SDS-PAGE and Western blotted with polyclonal Ab against C-terminus of TIE (lanes 1 and 2) or TEK (lanes 5 and 6) and then reprobed with SA-HRP (lanes 3, 4, 7, and 8). (B) Induction of autophosphorylation of TIE and TEK by rat postimmune IgGs against the extracellular domain of TIE or TEK. BaF/TIE (lanes 1 through 4) and BaF/TEK cells (lanes 5 through 8) were stimulated with medium alone (lanes 1 and 5), preimmune IgGs (lanes 2 and 6), 1 μg/mL postimmune IgGs (lanes 3 and 7), and 10 μg/mL postimmune IgGs (lanes 4 and 8). After 10 minutes of stimulation, cells were solubilized and proteins in lysates were immunoprecipitated with each MoAb. Immunoprecipitates were Western blotted with antiphosphotyrosine Ab (upper panels) and then reprobed with polyclonal Ab against C-terminus of TIE (lanes 1 through 4) or TEK (lanes 5 through 8; lower panels).