These responses suggest that, in primates, T cells are mainly downregulated as a whole (declines in common T cell markers such as TCR genes CD3D/E and CD247 [CD3Z], CD8, CD40LG and costimulatory molecule gene CD28), which along with dysregulation of several cell death/apoptosis genes such as FAS and CASPs, correlates with the bystander lymphocyte apoptosis seen during primate infection (10, 11, 16, 86, 89, 118), likely a filovirus-mediated mechanism meant to limit T cell antiviral responses. This evidence concerns the gene FAS and infection.