Increased frequency of circulating TrBs and decreased frequency of circulating FO B cells in patients with CTLA4 deficiency. Flow cytometric analysis of peripheral blood B-cell populations in patients with CTLA4 deficiency (n = 11) and healthy controls (n = 16). (A) Representative plots from a healthy control (left) and a patient with CTLA4 deficiency (right, homozygous CTLA4 3′ UTR mutation carrier), shown at 5% of events with gating strategy outlined (full description of B-cell gating strategy in supplemental Figure 1A). (B) Quantification of major B-cell subsets in the peripheral blood, including naïve, marginal zone (MZ), SWM, and DN populations as subset from total CD19⁺ B cells by the markers IgD and CD27. (C) Quantification of naïve (IgD⁺CD27^–) B-cell subsets in the peripheral blood, including T1/2, T3a, and T3b TrBs, resting mature FO B cells, aN B cells, and MZP B cells as further subsets by the indicated markers. For the CD45RB by CD21 and count by CD73 B-cell subset plots, final IgD⁺CD27^– B-cell frequency was derived as a percentage of the indicated parent gate. Symbols represent unique individuals; bars represent means (± standard deviation [SD]) of all data. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001 or as listed by 2-tailed Mann-Whitney U test. MZP, MZ precursor.