FAS and Autoimmunity: When the Th1/Th2 ratio is elevated, Th1 dominates the immune response, which not only promotes the increased release of IL-2, IL-6, TNF-α (52, 53), but also affects autoimmunity and stimulates the synthesis and release of chemotactic immunity factors from thyroid cells, thereby expanding autoimmune feedback (54–56) and accelerating the Fas-mediated apoptosis of thyroid cells (54).