As the co-regulatory receptors PD-1, Tim-3, and 2B4 have all been shown to be vital in regulating CD8+ T cell function, we assessed their expression on CMV/EBV-specific CD8+ T cells from patients with chronic hepatitis C (CHC) and healthy controls ex vivo and upon stimulation with virus-specific peptides in vitro. This evidence concerns the gene CD244 and cryohydrocytosis.