IDO1 and neoplasm: Hence, several ways exist to evade immune system-mediated tumor destruction: One way is modulation of cytokine secretion which restricts T cell infiltration, another one is immune escape by MHC-downregulation and a third one, which is likely to be responsible for immune escape in LP-DLBCL, is functional inhibition of infiltrating CD8-positive T cells by PD-L1- or IDO-mediated anergy [47].