IL21 and leukemia: To verify that the cellular processes and signaling cascades identified in Il21−/− AML mice are also modulated in Il21R−/− AML mice, we assessed CD11b expression on bulk leukemia cells as well as phosphorylation states of IKBα and p38-MAPK in L-GMPs from Il21R−/− and control Il21R+/−AML mice.