It appeared that, irrespective of the current smoking status among the TAO patients, a foundational increase was observed in the proinflammatory (IL-1β, TNF-α and IL-6), T helper (Th) 1 (IFN-γ and IL-12), Th2 (IL-4, IL-5 and IL-13), and Th17 (IL-17 and IL-23) cytokines in comparison with the non-, ex- and active smokers, which is indicative of the Th1 and Th2 cells involvement in the development of TAO. This evidence concerns the gene IFNG and thromboangiitis obliterans.