In RT-DLBCL, PD-1/PD-L1 interactions drive immune tolerance through bidirectional signaling: PD-1+ tumor B cells engage PD-L1+ histiocytes and dendritic cells, while PD-L1 expression on T cells further dampens cytotoxic activity [88,89]. The gene discussed is CD274; the disease is diffuse large B-cell lymphoma.