Schematic figure of LFA-1-specific antibody binding sites and the cross-talk from LFA-1 to α₄β₁. (A) A schematic picture of LFA-1 α_L and β₂-chains, with the binding sites of the antibodies used. Antibodies in red induce the inhibitory signal to α₄β₁; antibodies in blue do not affect α₄β₁ activity. Binding site for talin and 14-3-3 indicated on the β₂ chain. (B) Activation from the T-cell receptor, through chemokines or by LFA-1 antibodies, results in PLC and PKC activation and phosphorylation of Thr-758 in β₂, followed by binding of 14-3-3 and Tiam1 and activation of Rac1. The signal is further transferred to α₄β₁, resulting in dephosphorylation of Thr-788/789 and loss of activity and ligand binding.