CTLA4 and lymphoma: To determine if PD-1/CTLA-4 blockade preferentially affects the ability of T cells to kill latently- versus lytically- infected lymphoma cells, we examined the number of EBER positive cells by in situ hybridization, and performed IHC using antibodies to detect the EBV-encoded EBNA2, LMP1, BZLF1 and BMRF1 proteins.