However, it is worth pointing out that (i) in a limited number of experiments, we failed to detect any IL-2 production from these activated CD8 T cells after dengue virus peptide stimulation in vitro and (ii) from the other studies, we infer that the frequency of TNF-α-producing cells is also likely to be very low in dengue patients, on the order of 0.1 to 3% of the total CD8 T cells, which is not substantially different from the low frequency of IFN-γ-producing cells that we have seen in our dengue patient cohort (5). Here, CD8A is linked to dengue disease.