Fig. 3

For T cell activation, both stimulatory signal 1 and 2 are needed. Signal 1 consists of the interaction between the major histocompatibility complex on the dendritic cell and the T cell receptor. Different combinations of interactions are possible for signal 2. One inhibiting signal 2 is the interaction between programmed death receptor 1 (PD-1) on T cell and programmed death ligand 1 (PD-L1) on tumour cells or antigen presenting cells. a T cell activation is blocked by an inhibiting signal 2 between PD-L1 and PD-1 receptor binding. b When an anti-PD1 antibody is used, the inhibiting signal of the T cell is blocked whereby an activation signal of the T cell is gathered and the T cell is activated