Emodin was purchased from Beijing Solarbio Science & Technology Co., Ltd. IL-2 (cat. no. SRP3242) and anti-CD3 (cat. no. SAB4700040)/CD28 (cat. no. SAB4700739) were purchased from Sigma-Aldrich; Merck KGaA. Caerulein was obtained from MedChemExpress. Meanwhile, ARJ21 cells were treated with 20 and 40 µM Emodin, according to previous references (28 (link),29 (link)).