IL6 and infection: Our findings of early deficiency in the immune system post-infection, which correspond to changes within the brain, are consistent with those of Gopalakrishnan et al., who detected increased IL-6 expression and other proinflammatory responses in the brain as early as 7 days of SIV infection, possibly indicating that the early SIV infection in the brain is characterized by significant macrophage infiltration and astrocyte activation (24).