In this report, we have used a new cord blood-humanized mouse model to show that EBV-infected B cells express inhibitory ligands (PD-L1 and PD-L2) for the PD-1 T cell receptor, and to demonstrate that blockade of the PD-1/CTLA-4 inhibitory T cell receptors enhances the ability of T cells to control growth of EBV-induced lymphomas in this model. This evidence concerns the gene PDCD1 and lymphoma.