Alteration of STAT3 and Erk signaling in B cells from cGVHD patients. (A) Whole PBMCs from AHSCT recipients with no GVHD, active cGVHD, and healthy donors were left unstimulated (medium alone, left) or stimulated with CpG-B 10 μg/mL for 2 hours at 37°C (right), fixed, permeabilized, and incubated with anti-CD19 and phospho-Erk 1/2 mAbs. Phospho-Erk MFIs in CD19⁺ cells are shown at baseline (left) and after CpG stimulation as a ratio activated/baseline phospho-Erk MFI (right). (B) Representative histograms of phospho-Erk MFI in CD19⁺ cells at baseline (blue), after CpG stimulation (red), isotypic control (yellow) in an AHSCT recipient with no GVHD and a cGVHD patient. (C) Whole PBMCs from AHSCT recipients with no GVHD, active cGVHD, and healthy donors were left unstimulated (medium alone, left) or stimulated with recombinant human IL-21 200 ng/mL for 2 hours at 37°C (right), fixed, permeabilized, and incubated with anti-CD19 and phospho-STAT3 mAbs. Phospho-STAT3 MFI in CD19⁺ cells are shown at baseline (left) and after IL-21 stimulation as a ratio activated/baseline phospho-STAT3 MFI (right). (D) Representative histograms of phospho-STAT3 MFI in CD19⁺ cells at baseline (blue), after IL-21 stimulation (red), isotypic control (yellow) in an AHSCT recipient with no GVHD and a cGVHD patient.