Flow cytometric analysis of blood B-cell subsets in healthy controls and CVID patients. All B-cell subsets are determined within the CD19⁺ lymphogate. Naive B-cell subsets (transitional B cells and naive mature B cells) are defined within the CD27⁻IgD⁺ lymphogate based on expression of CD24 and CD38. (A) Healthy controls. (B-F) B-cell patterns observed in CVID patients. (B) B-cell pattern 1: low transitional and memory B cells. (C) B-cell pattern 2: low naive mature, marginal zone–like, and memory B cells. (D) B-cell pattern 3: low marginal zone–like and memory B cells. (E) B-cell pattern 4: low memory B cells. (F) B-cell pattern 5: normal marginal zone–like and memory B cells. Naive mature B cells cells in CVID patients (B-F) were more often CD38^low compared with controls (A) and represent, at least in part, the CD21^lowCD38^low B-cell population within the naive B-cell compartment.