CTLA4 and non-Hodgkin lymphoma: Assessment of immune checkpoint proteins revealed high expression of PD-L1, CTLA-4 (CD152) and IDO in all tumors, while levels of lymphocyte activating gene 3 (LAG-3) and PD-1 were below 20% in both NHL and GIT, with a tendency towards higher expression in the latter (Figure 3A, right chart).