Increased release of immature K-RAS^G12D–expressing myeloid cells in the setting of Rce1 deficiency. (A) White blood cells were evaluated in blood smears from Rce1^fl/flK^LSLM (▪; n = 6) and Rce1^fl/+K^LSLM mice (□; n = 6) harvested before and after pI-pC injections. Immature cells (myeloblasts, promyelocytes, promonocytes, myelocytes, metamyelocytes, band cells, pelgeroid cells) (A) and lymphocytes (B) are plotted as percentages of total white blood cells. Differences between Rce1^fl/flK^LSLM and Rce1^fl/+K^LSLM mice were evident 3 weeks after pI-pC injection, and the proportions did not change over time. Thus, data from 3, 5, and 7 weeks were combined. (C) Photographs of blood smears from before and 5 weeks after pI-pC injections (magnification: 100×/1.30 NA oil-immersion objective lens). (Top right panel) Arrowhead, pelgeroid cell; arrow, band cell; large cell in center, myeloblast.