CSF1 and neoplasm: In addition, when the effects of CSF1 were neutralized upon exposure to an anti-CSF1 receptor neutralizing antibody in tumour-bearing ApcMin/+ mice, we observed a strong reduction in the number of both F4/80hiMHCIIlow and F4/80hiMHCIIhi tumour-resident macrophages, whereas the numbers of monocytes and monocyte-derived macrophages were unperturbed (Fig. 7b).