Fig. 2.

Although required for T-cell activation, the antigen-T-cell receptor interaction does not govern the fate of the T cell. Positive costimulatory molecules, such as CD28, 4-1BB, inducible costimulator, and OX40 can stimulate a T-cell response specific for the antigen presented. On the other hand, negative costimulatory molecules, such as CTLA-4, B7-H1/PD-1. B7-H4, and BLTA can inhibit T-cell activation, and may induce anergy (tolerance) to the presented antigen. (Color version of figure is available online.)