Figure 2.

SpeB2 (RGD containing) binds to integrin α_vβ₃ or α_IIbβ₃ expressed on mammalian cells. (A) Binding by untransfected cells (hatched bars) or transfected cells expressing α_vβ₃ (solid bars) to microtiter wells coated with buffer alone or with the indicated protein was determined (see Materials and Methods). Data shown are the means and SD of quadruplicate samples. (B) (Left) α_vβ₃-transfected cells were incubated with anti-α_vβ₃ mAb, anti-α_Macβ₂ mAb, or buffer alone before binding to mSpeB2. (Right) Control mouse ascites or ascites containing mAb 2A3-B2-C12 directed against amino acid residues 302–308 of SpeB were added before cell binding to mSpeB2-coated wells at the indicated concentrations. The means and SD of quadruplicate samples are shown. (C) Binding by untransfected cells (hatched bars) or transfected cells expressing functional α_IIbβ₃ (solid bars) to microtiter wells coated with the indicated protein was determined. Data are expressed as the means of duplicate samples. (D) Transfected cells expressing functional α_IIbβ₃ were incubated with anti-α_IIbβ₃ mAb, anti-α_Macβ₂ mAb, or buffer alone before binding to mSpeB2. Alternatively, control mouse ascites or ascites containing mAb 2A3-B2-C12 directed against amino acid residues 302–308 were added to mSpeB2-coated wells at the indicated concentrations before cell binding. Shown are the means and SD of quadruplicate samples. CMA, control mouse ascites; 1:1K, 1:1,000 dilution; 1:10K, 1:10,000 dilution.