Deficiency of RORγt mRNA in HIES patients. (A) RORγt mRNA expression in CD4⁺ cells activated for 2 d with CD3/CD28/IL-2 in five HIES patients and five normal controls. (B) RORγt mRNA expression after 2 d of culture is proportional to the number of Th17 cells as determined by intracellular cytokine expression after 4–5 d.