The plasma of case 28 contains nonneutralizing autoantibodies against GM-CSF. (A) The autoantibodies against GM-CSF were detected by indirect ELISA with serially diluted plasma. C.B., coating buffer only; HC, healthy control. (B) GM-CSF neutralizing activity of the plasma was performed by STAT-5 phosphorylation (pSTAT-5) assay with peripheral blood mononuclear cells from healthy volunteers. IL-3 treatment was used as a positive control for pSTAT-5. Plasma from one anti–GM-CSF autoantibody patient served as positive control (Kuo et al., 2017). The assays were performed in duplicate independently. NA, not activated.