These results were confirmed using ex vivo human CD4 T cell populations. Human PBMC were stimulated with SEB, and AR and other cytokines measured by intracellular staining. Naive cells (CD45RA+) expressed high levels of IL-2 and AR, but very low levels of either IFNc or IL-4 (data not shown). Memory cells produced all cytokines tested, at varying frequencies. To determine whether AR expression was associated positively or negatively with subset-specific cytokines, the frequencies of cells expressing AR plus each of the other cytokines were measured from the ICS results. These values were then compared with the double-producing frequencies predicted for random association of each cytokine pair, by multiplying the individual frequencies for each cytokine. Figure 5B shows that AR was expressed in association with TNFa, IL-2, IFNc, IL-4 and IL-17 at slightly higher frequencies than predicted by random association. Similarly, TNFa and IL-2 showed positive associations with all other cytokines. In contrast, the subset-specific cytokines IFNc, IL-4 and IL-17 showed mostly negative associations between each other, as expected. These results were confirmed at the RNA level by sorting SEB-stimulated human PBMC according to surface AR expression. Both AR+ and AR-memory CD4 T cell populations expressed similar levels of IL-4 and IFNc as measured by RT-PCR ( Figure 5C ). IL-2 mRNA levels were higher in AR+ T cells, in both CD45RA-and CD45RA+ cells.