Response to luspatercept treatment of patients with MDS-SR is associated with CTL baseline activation. (A) Overall response rate in patients with MDS-RS undergoing luspatercept treatment at T1. Gray, purple, and blue levels indicate major response in HTB, minor response in HTB, and HI in LTB, respectively. (B-E) Purple, green, and orange columns indicate data obtained in healthy CTRs, MDS-SR responders, and MDS-SR nonresponders, respectively. (B,D) CD54 expression level in circulating CTLs of patients with MDS-SR at T0 (B) and T1 (D). (C,E) Percentage of circulating mMDSCs in patients with MDS-SR at T0 (C) and T1 (E). For statistical evaluation details, see the supplemental Materials. HI, hematological improvement; HTB, high transfusion burden; LTB, low transfusion burden; NR, nonresponder; ORR, overall response rate; R, responder.