Although a number of reports have described natural suppressor (NS) myeloid cells in BM from non-tumor bearing animals [11], [12], most studies during the last 20 years have focused on tumor-associated myeloid-derived suppressor cells and suggest that BM-derived CD11b+ GR-1+ immature myeloid cells (IMCs) in normal, tumor-free mice lack immunosuppressive activity [8], [13]. This evidence concerns the gene ITGAM and neoplasm.