Compared with the Pre-CRT group, the CD3+ T cells (p = 0.018), CD4+ T cells (p < 0.001), NK cells (p = 0.009), and CD4+/CD8+ ratio (p < 0.001) in the peripheral blood of patients with ESCC after CRT were significantly reduced, and CD8+ T cells were significantly increased compared with those before CRT (p < 0.001). Here, CD4 is linked to esophageal squamous cell carcinoma.