PDCD1 and lymphoma: To examine the effect of PD-1/CTLA-4 blockade on T cell infiltration of tumors, EBV-induced lymphomas in PD-1/CTLA-4 antibody-treated animals, versus untreated animals, were formalin fixed, paraffin-embedded and then examined by H & E and immunohistochemistry (IHC) staining using antibodies directed against B cell and T cell markers.