CD47 is a protein that acts as a “don’t-eat-me” signal to immune cells called macrophages. Normally, macrophage cells will consume and destroy cells that are damaged, infected or cancerous. But most cancers display a large amount of CD47 protein, which protects the cancer from attack by the body's immune system. Blocking the CD47 signal using custom-tailored antibodies can help the macrophages attack and destroy cancer cells.
stemcell.stanford.edu/news/pedsCD47.html 
