However, the importance of CD4+ and CD8+ T cells in central nervous system disease in animal models of neuroinvasive infection is unclear, with one study demonstrating these cells assist in clearance from the central nervous system of mice while another demonstrated protection from lethal encephalitis following knock-out of CD4+ T cells and CD8+ T cells (Rowell and Griffin, 2002; Brooke et al., 2010). The gene discussed is CD4; the disease is viral encephalitis.