Basophil development and turnover. (A) Expression of surface markers on developing basophils. Dot plots of embryonic day 16.5 fetal liver samples from 4get mice were gated on Ter119^-−Siglec-F⁻ cells to gate out eosinophils (Siglec-F⁺) and erythroblasts (Ter119⁺), whereas bone marrow cells and splenocytes were gated on CD4⁻ and Siglec-F⁻ cells in a FSC^loSSC^lo gate that excludes mast cells (Figure S3). Since Th2 cells, natural killer (NK) T cells, eosinophils, mast cells, and basophils are the only cell types that express IL-4/eGFP in 4get mice, this gating strategy leaves only basophils in the IL-4/eGFP⁺ population. The experiment has been repeated with comparable results. (B) Frequency of basophils (defined as indicated in Figure S5) in bone marrow (BM), spleen (SP), blood (BL), and lung (LU) of 4get mice before (□) or 9 days after (■) infection with N brasiliensis. (C) Detection of incorporated BrdU in basophils (IgE^hi cells) of BALB/c mice by flow cytometry. For panels A and C, the numbers in the quadrants indicate the frequency of each population. (D) BrdU incorporation in basophils (IgE⁺B220⁻ cells) of naive (left) or N brasiliensis–infected BALB/c mice (right) at indicated time points after BrdU administration with 3 to 5 mice per group. The graphs show pooled results from 2 independent experiments. Each dot represents 1 mouse. (E) Kinetics of disappearance of transferred basophils from 4get mice in naive (left) and N brasiliensis–infected BALB/c mice (right). Graphs show the mean plus or minus SD of 3 individual mice from 2 independent experiments. (F) Decline of transferred basophils in the lung of N brasiliensis–infected BALB/c mice. The graph shows the mean of 2 mice per timepoint.