Antigen recognition (1) Ag recognition 1)+costimulatory(2) APC VACM-1 LFA-3 ICAM-1 MHC class Il B7 molecules CD4 TCR-CD3 complex CD28 LFA-1 CD2 2) VLA-4 Th Anergy Activation and Proliferation Peripheral tolerance is induced when mature lymphocytes recognize antigens without adequate levels of the costimulatorsPeripheral tolerance is induced when mature lymphocytes recognize antigens without adequate levels of the costimulators