In spleen, neutrophil numbers were largely normalized in aged Lyn−/−G‐CSF−/− mice, being similar to those of C57BL/6 mice and augmented above the neutropenia of G‐CSF−/− mice; however, they remained significantly below the neutrophil expansion observed in aged Lyn−/− mice (Figure 1D,E). This evidence concerns the gene CSF3 and neutropenia.