Distinct circulating cytokine levels in different types of rejection. Serum levels of IL-2, IL-4, IL-6, IL-10, IL-17, and IL-21 (A–F) in patients in NR (n = 30), TCMR (n = 28) and ABMR (n = 8) cohorts were measured before anti-rejection therapy. Dash dot line represents the mean value. *P < 0.05, **P < 0.01, and ***P < 0.001. IL, interleukin; ABMR, antibody-mediated rejection; NR, non-rejection; TCMR, T cell-mediated rejection.