CD27⁺ B cells predominate in the cGVHD group with progressive disease 2 years after rituximab. (A) Representative flow cytometric profile of B-cell subsets characterized by relative IgD versus CD38 staining in a patient with stable/improved cGVHD versus unresponsive cGVHD 2 years after rituximab. (B) Box plots showing the differences in frequencies of B-cell subsets a and b between the stable/improved and rituximab-unresponsive cGVHD groups. (C) Representative CD27 flow cytometric analysis of CD27 positivity of gated CD19⁺ B cells.