Figure 1.

ICPI mechanisms. (A) The principal pathway of co-stimulation for activation of naïve T lymphocytes is the CD28/B7 pathway, consisting of an activating signal for T lymphocytes following binding of CD28 to B7. CTLA-4 can block this stimulatory pathway. Other inhibitory signals induced by binding of PD-1/PD-L1 occur in the lymph nodes and at the tumor site. (B) The principal treatments currently used are based on inhibition of CTLA-4 and/or of the PD-1/PD-L1 pair. This inhibition which results in prolonged activation of T lymphocytes directed against tumoral neoantigens, aims to neutralize tumor cells.