CD47−/− tumors also exhibited a higher level of regulatory T cell (T-reg) (Fig. 1h), Ki67+ proliferating T cell and natural killer (NK) cell (Fig. 1i) infiltration when the tumors grew to a size of 500–600 mm3, suggesting that there is a phase of tumor growth when the host immune system responds to the CD47+/+ and CD47−/− tumors differently. This evidence concerns the gene CD47 and neoplasm.