Oneliner_1417

OneLiner

Two signals are required for T cell activation. Signal 1 is the antigen that is presented to the T cell receptor (TCR) by an APC’s MHC class II. Signal 2 is known as the co-stimulatory signal, and this occurs via the interaction of B7 protein (CD80/86) on the APC and CD28 on the T cell. This leads to T helper cell activation.