PDCD1 and myelodysplastic syndrome: As compared with normal controls, CD4+CXCR5+ TFHs and CD4+CXCR5+PD1+ TFHs were markedly elevated in patients with AA (7.33% [1.69-13.23] vs. 1.82% [0.60-5.22], P = 0.0011 and 3.44% [0.78-8.49] vs. 0.96% [0.56-1.92], P = 0.0006, respectively; Figure 2D) or MDS (3.65% [1.80-10.05] vs. 1.44% [0.44-2.75], P = 0.0181 and 2.29% [1.38-3.58] vs. 1.15% [0.33-1.99], P = 0.0284, respectively; Figure 2E).