IFN-1 inhibited growth of primary human erythroid cells and impaired EPO/EPOR signaling in vitro. (A) Growth curves of human erythroid cells in the absence or presence of human IFNα at indicated concentrations (N = 3). (B-C) Representative western blot and quantitative analyses of STAT2 levels in day 6 erythroid cells cultured in the absence or presence of human IFNα at indicated concentrations (N = 3). (D-E) Representative western blot and quantitative analyses of pSTAT5 levels in day 6 erythroid cells cultured in the absence or presence of human IFNα at indicated concentrations (N = 3). (F) Quantitative analyses of CISH mRNA levels in the absence or presence of human IFNα. (G-H) PCR result and Sanger sequencing analysis of CISH in the CB-iEry cells with or without CRISPR/CAS9-mediated CISH KO. (I) Growth curves of CB-iEry cells with or without CISH knockout (KO) in the absence or presence of human IFNα at indicated concentrations (N = 3). (J) Representative western blot and quantitative analyses of pSTAT5 levels in CB-iEry cells with or without CISH KO in the absence or presence of human IFNα (500 U/mL) or EPO (5 U/mL) (N = 3). ∗P < .05; ∗∗P < .01; ∗∗∗P < .001.