GFP and HGAL expression in Rosa26^HGAL mice. (A) Fluorescence-activated cell sorting analysis of GFP (HGAL) expression in peripheral blood B-cell populations in nonimmunized Rosa26^HGAL/Aid-Cre mice (n = 6), Rosa26^HGAL/Mb1-Cre mice (n = 6), and Rosa26^HGAL/Sca1-Cre mice (n = 6) (left panels). GFP expression in B220⁺IgM⁺ and B220⁺IgM⁻ B cells (middle panels). Bar graph showing the percentages of B220⁺ lymphocytes in peripheral blood from Rosa26^HGAL, Rosa26^HGAL/Aid-Cre, Rosa26^HGAL/Sca1-Cre, Rosa26^HGAL/Mb1-Cre, and control WT mice (n = 6 each) (right panel). There were no statistically significant differences among the animals. (B) GFP expression in the spleen of Rosa26^HGAL/Aid-Cre mice before and after immunization (left panels). Expression of HGAL and GFP in Aid-Cre mice requires initiation of an immune response and GC formation. Graphs show GFP expression in GCB cells before and after immunization (right panels). (C) Western blot analysis using extracts from Rosa26^HGAL/Sca1-Cre (n = 3) and Rosa26^HGAL (n = 3) splenic B cells and the indicated antibodies.