The absolute number of Th17 cells correlated negatively with C3 in TA patients (r = −0.625, p = 0.002).There was no significant correlation with PLT, IgG, IgA, IgM, C4, ESR, CRP, NIS, vascular stenosis, IL-6, IL-10, IL-17, or TNF-α (p >0.05). The gene discussed is IL17A; the disease is Takayasu arteritis.