CTLA4 and neoplasm: In this study, we examined the immune system in patients with progressively growing head and neck cancer and we compared T cells isolated from the tumor vs the peripheral blood (PBL) for the expression of co-stimulatory and co-inhibitory receptors, OX40, programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4).