Frequency and proliferation history of CD21^low B cells in CVID patients. (A) CD21^low B cells are depicted as proportions of CD19⁺ B cells and compared with healthy controls (c) according to their B-cell subset pattern. Individual data points are displayed and bars indicate medians. B-cell patterns were compared with controls using the Mann-Whitney test. (B) Number of cell divisions and frequency of SHMs of sorted CD21^lowCD27⁻IgM⁺IgD⁺ naive B cells compared with sorted CD21⁺CD27⁻IgM⁺IgD⁺ naive B cells in patients with > 20% CD21^low B cells and a naive B-cell replication history of > 4 cell divisions.