PDL1^hiB cells are decreased in patients with cGVHD and increased after anti-CD20 rituximab treatment. (A) PD-L1 expression on CD19⁺ live peripheral blood mononuclear cells yields 3 distinct populations (PD-L1^lo, green; PD-L1^int, blue; and PD-L1^hi, red); the number adjacent to the gates defines the percentage of total live CD19⁺ cells. The graph depicts median fluorescence intensities (MFI) of PD-L1 on CD19⁺ cells. Data are representative of 16 patients (median, range). (B) CD19⁺ PD-L1^hi cells as a proportion of total live CD19⁺ cells (mean, standard error of the mean). (C) Naive CD19⁺ B cells as a percentage of total live CD19⁺ cells in healthy donors (HD) in allo-SCT recipients with no cGVHD, at diagnosis of cGVHD and at 12 months after the diagnosis of cGVHD and rituximab treatment (mean, standard error of the mean). (D) Absolute values of naive CD19⁺ B cells (mean, standard error of the mean). (E) PD-L1^hi cells as a percentage of total live naive CD19⁺ B cells (mean, standard error of the mean). (F) Absolute values of PD-L1^hi naive CD19⁺ B cells (mean, standard error of the mean). MZ-like, marginal zone-like; ns, not significant.