Consistent with previous reports [23], [24], SIVmac251 infection induced a decrease in blood CD4+ and CD8+ T-cell and NK-cell counts, detectable by D7 p.i., but reaching their nadir on D14 p.i., with reductions of 53% for CD4+, 49% for CD8+ and 85% for NK cells (Table 1). Here, CD4 is linked to infection.