JAM-A is a Csk-binding protein. (A) Representative anti-Csk immunoblots of proteins immunoprecipitated with anti–JAM-A or IgG₁ from lysates of human platelets exposed to immobilized Fg or BSA. (B) Quantitation of normalized optical density of “A” from 3 independent experiments (P = .05). (C) Representative anti-Csk immunoblots of immunoprecipitated proteins with anti–JAM-A or control IgG₁ from lysates of human platelets exposed to immobilized BSA or Fg for 60 minutes. In (A,C), blots were reprobed with anti–JAM-A to ensure equal loading. (D) Quantitation of normalized optical density of “C” from 3 independent experiments (P = .0009).