Reduced IL-10 and IL-17 production by ICOS-deficient T cells after in vitro stimulation. Bar graphs show in vitro cytokine production of isolated CD4⁺ T cells after stimulation with the indicated stimuli for 5 ICOS-deficient patients (ICOS) and 5 healthy control subjects (HD). Bars display mean and standard deviation for each cohort. Statistical significant differences are indicated (*P < .05; **P < .001).