To determine if infection with HSV-1 favours the infiltration of immune cells bearing Fas and FasL into the CNS at the peak of primary infection, we performed flow cytometry analyses of the brain and trigeminal ganglia at day 8 p.i. and assessed the presence of Fas and FasL on CD4+ T cells (CD3+/CD4+ cells), CD8+ T cells (CD3+/CD8+ cells) and monocytes (CD45hi+/CD192+/CD11b+/Ly6C+ cells). This evidence concerns the gene CD4 and infection.