PRF1 and myelodysplastic syndrome: The perforin and granzyme B in CD8+ T cells purified from MDS patients (n = 9, samples: 026‐028, 034, 036, 037 and 045‐047) were significantly lower after co‐cultivation with excess exogenous Gal‐9 than those in CD8+ T cells alone and were partially restored by TIM3 inhibitor or Gal‐9 inhibitor (perforin%: i: 15.33 ± 2.83% vs a: 21.79 ± 3.35% vs j: 20.63 ± 3.37% vs k: 19.01 ± 3.49%, P < .0001****; granzyme B%: i: 15.95 ± 5.47% vs a: 21.32 ± 6.56% vs j: 20.18 ± 6.44% vs k: 18.38 ± 6.07%, P = .0019**) (Figure 5A‐C).