CCL21 and hematocrit: Through immunostaining of FSP1 (Fibroblast-specific protein 1) and ACTA2 combined with in situ hybridization of CCL21, FSP1+CCL21+ fibroblasts or myofibroblasts are easily observed in germinal centers (Fig. 6a), area of lymphocyte aggregates (Fig. 6c) or adventitia of vessels (Fig. 6c, white arrows), as well as the area of intact thyroid follicular structures with few lymphocytic infiltration (Fig. 6b) in the thyroid tissues of HT patients.