HIES patients have a defect in the generation of IL-17–producing CD4⁺ T cells in vivo. Intracellular expression of IL-17A and IL-2 in purified CD4⁺ T cells from a healthy donor (A) and a HIES patient (B) activated for 5 d (see Materials and methods). (C) The frequency of IL-17A⁺ cells, determined by intracellular cytokine expression, and (D) IL-17A secretion by CD4⁺ T cells from five healthy donors and five HIES patients that had been stimulated with anti-CD3 mAb, anti-CD28 mAb, and IL-2 for 4–5 d, as determined by ELISA. Each symbol represents the value from an individual donor or patient, and the line represents the mean. (E) Time course of IL-17A secretion by CD4⁺ T cells isolated from a normal donor and HIES patient. Similar results were obtained when CD4⁺ T cells from all HIES patients were examined over a culture period that continued for up to 11 d. (F and G) Expression of IL-22 mRNA (relative to housekeeping genes; F) and secreted protein (G) by normal and HIES CD4⁺ T cells was determined after 2 and 5 d, respectively, of stimulation with CD3/CD28/IL-2. *, P < 0.05; **, P < 0.01.