Precursor B cells in CVID bone marrow. Altered B-cell precursor composition in BM biopsies of CVID patients grouped according to the Freiburg classification.¹⁴  (A) Two examples showing the flow cytometric analysis of bone marrow samples from CVID patients with normal (left panels) and disturbed (right panels) B-cell precursor development. CD19⁺ events were gated using CD3/CD16/CD33 as exclusion markers. B-I indicates pre-B-I; B-II, pre-B-II; and B-Im + B-Ma, immature plus mature B-cell populations. (B) B-cell precursors were phenotypically differentiated into pro-B, pre-B-I, pre-B-II, and immature B cells by flow cytometry as described in “Phenotyping of peripheral blood lymphocytes and of precursor B cells in BM aspirates.” Presented are B-cell precursor analyses of BM aspirates from controls (Co, ○, n = 13) and of CVID patients grouped according to the Freiburg classification Ia (●, n = 12), Ib (▴, n = 12), or II (□, n = 1). Lines indicate median values; statistical differences between controls and patient groups were tested by the Wilcoxon test. ns indicates not significant. (C) The percentage of pre-B-I precursors in bone marrow samples of CVID patients is plotted against the absolute peripheral B-cell counts. Symbols represent CVID subgroups as depicted in panel B. For the whole CVID group, the Spearman rank order correlation test yielded a statistically significant (P < .001) correlation coefficient of −0.67. For a separate analysis of group Ib, the correlation coefficient was 0.78 (P = .004), whereas for the group Ia the correlation did not reach statistical significance.