Loss of p65 results in the accumulation of HSPCs in the spleen. (A) Splenocytes from wild-type or p65^hem−/− mice were analyzed for HSC frequency using flow cytometry. (B) The average number of cells per genotype is displayed (n ≥ 7). (C) Myeloid progenitors from wild-type or p65^hem−/− mice were analyzed by flow cytometry. (D) The average number of cells per genotype is displayed (n ≥ 7). (E) Spleens from wild-type or p65^hem−/− mice were stained with hematoxylin and eosin for histological analysis. The arrow indicates a region of extramedullary hematopoiesis. Image is representative of staining from 3 different animal per genotype. (F) Average weight of spleens from wild-type or p65^hem−/− mice are displayed (n ≥ 10). *P ≤ .005.