CTLA4 and infection: For example, infection with HIV or the hepatitis C virus increases the expression of a number of negative co-stimulatory molecules, including lymphocyte activation gene-3 (LAG-3), CD160, cytolytic T-lymphocyte antigen-4 (CTLA-4), T-cell immunoglobulin mucin-containing domain-3 (TIM-3), and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) [32,33].