Hyper-IL6 stimulates the formation of granulocyte clusters in vitro. (A) Hyper-IL6 (•) and mIL6 (□) were compared directly for their ability to generate granulocyte clusters from the bone marrow of G-CSF^−/−/GM-CSF^−/− mice. Results are plotted as molar concentration vs the number of granulocyte-containing clusters generated after 4 days in liquid culture. (B,C) Typical clusters arising from bone marrow cultures stimulated with Hyper-IL6 (B) or IL6 (C). The images have been cropped to show a single cluster, and were acquired as in Figure 3A.