It is likely that the estimate of CTL killing in HIV-1 infection, calculated by Wick et al [7], is also an overestimate of the natural killing rate of CD8+ T cells in the unmanipulated system because it is an order of magnitude higher than the total death rate attributable to all causes (including CD8+ T cell killing, activation induced cell death and any cytopathic effect of HIV-1), which has been estimated at 0.7–1 d−1[17]. Here, CD8A is linked to HIV-1 infection.