CVID and RA patients may display an increased frequency of CD21^−/lo B cells in their blood. (A) CVID group Ia patients were previously defined as patients displaying a frequency of CD21^−/lo naive B cells > 20% of total B cells.²¹  Each diamond represents a person and (B) dot plots show CD19 and CD21 expression on CD27⁻-gated peripheral B cells from representative CVID group Ia patients. (C) Increased CD21^−/lo B-cell frequency in RA patients. Dot plots show CD19 and CD21 expression on CD27-depleted peripheral B cells from a representative healthy donor (HD10) and RA patients. (D) The frequencies of CD21^−/lo naive B cells are compared between healthy donors and RA patients. Each diamond represents a person and statistically significant differences are indicated.