NKM mice exhibit massive hepatosplenomegaly, extramedullary hematopoiesis, and increased autonomous and granulocyte-macrophage colony-stimulating factor–induced colony growth of splenocytes. (A) Spleen and (B) liver weight (relative to total body weight [bwt]) in NKM (n = 9), KM (n = 7), NM (n = 4), and Ctr (n = 7) 3 weeks after pI-pC injections. (C) Representative flow cytometry plots of splenocytes with antibodies recognizing CD34, CD117, CD11b, and Gr-1. Mean percentage of double-positive splenocytes from NKM (n = 6), KM (n = 3), NM (n = 1) and Ctr (n = 3) mice is indicated. (D) Granulocyte-macrophage colony-forming unit colony-forming ability of splenocytes isolated from NKM (n = 3), KM (n = 3), NM (n = 2) and Ctr (n = 3) mice 3 weeks after pI-pC injections. The number of colonies formed from NKM splenocytes was significantly increased compared with the other genotypes at all granulocyte-macrophage colony-stimulating factor (GM-CSF) concentrations (P < .05). Data are mean and SEM; statistics: 1-way analysis of variance and Tukey posthoc test. (E) PCR amplification of genomic DNA from individual granulocyte-macrophage colony-forming unit colonies. (F) Western blots of extracts from serum-starved and GM-CSF–stimulated BM cells from NKM (n = 2; pooled), KM (n = 1), NM (n = 4), and Ctr mice (n = 5). Actin was used as a loading control. Densitometry of protein bands was determined with the Quantity One software (Version 4.4.0; Bio-Rad).