Response to Comment on “HIV-Specific IL-21 Producing CD4⁺ T Cells are Induced in Acute and Chronic Progressive HIV Infection and Are Associated with Relative Viral Control”

We agree with Drs. Iannello, Samarani, and Ahmad that staphylococcal enterotoxin B stimulation will not activate all T cell subsets, but only the vbetas associated with staphylococcal enterotoxin B activation, thus possibly explaining the discordance in results between our group and that of Iannello et al. (1). It should also be noted, however, that ionomycin stimulation alone also may not be a physiological stimulus that provides two signals to T cells, as a phorbol ester such as PMA is often required in conjunction with Ca ionophores to accomplish this (2). The data in Fig. 4B (3) do not quantify the numbers of IL-21 producing cells between the two groups but show that, within the IL-21 producing populations observed, they are enriched more for CCR7⁻CD45⁻ cells in HIV-infected individuals.