D-F: Primary humanCD4T cells were transfected with control or FIP3.1 siRNA. D, E: Cells were allowed to spread on poly-lysine-coated coverslips for 5 min. Intracellular Lck was detected by immunofluoresecence. D: A single optical section at the level of the contact surface is shown. Bar, 10 µm. E: Population analyses of the spreading area of cells at the level of the contact surface. 