Hhex deletion results in loss of B-cell progenitors. (A) Flow cytometric analysis of the BM of Hhex^+/fl and Hhex^−/Δ mice showing absence of Pre-Pro (B220⁺CD19⁻), Pre- and Pro-(B220⁺IgM⁻) and mature (B220⁺IgM⁺IgD⁻) B cells. (B) Combined data showing total number of B-cell progenitors in the BM of mice of the indicated Hhex genotypes, analyzed as in (A). Data were calculated by multiplying population frequencies from flow cytometry with the total cell counts. Data are mean + standard deviation. (C) Loss of transitional B cells in the spleen of Hhex^−/Δ mice. Flow cytometric analysis showing loss of T1 to T3 and follicular (FOL) B-cell subtypes, but relatively normal numbers of marginal zone (MZ) and marginal zone precursor (MZP) B-cells. (D) Combined data showing total number of splenic B-cell subsets in mice of the indicated Hhex genotypes, analyzed, as in (C). *P < .05; **P < .01; *** P < .001 by Student t test.