Most pronounced distortion of B-cell homeostasis in cGVHD patients with hypogammaglobulinemia. (A) Percentages of CD19⁺CD21^low immature B cells are significantly elevated in cGVHD patients and mainly in the cohort with hypogammaglobulinemia. Lines indicate the range of CD19⁺CD21^low immature B cells in healthy persons (2%–7%). Data are shown as box plots. (B) CD19⁺CD21^int-highCD38^highIgM^high transitional B cells are significantly higher in cGVHD patients with hypogammaglobulinemia compared with the normogammaglobulinemia cohort. The line indicates the normal upper range of these cells in healthy persons. Data are shown as box plots. ○ represents outliers. (C) Significantly lower absolute numbers of CD19⁺CD10⁻CD27⁻CD21^high naive B cells in cGVHD patients with hypogammaglobulinemia compared with the hypergammaglobulinemia and normogammaglobulinemia cohort. We observed a mean percentage of 85 in cGVHD patients compared with 50% of CD19⁺CD10⁻CD27⁻CD21^high naive B cells in healthy persons. Data are shown as box plots. (D) CD19⁺CD27⁺IgD⁺ non–class-switched memory B cells are significantly lower in cGVHD patients with hypogammaglobulinemia compared with the hypergammaglobulinemia and normogammaglobulinemia cohort. Data are shown as box plots.