I think the key is that Cancerous cells expressed a higher level of this marker leading the Immune cells to destroy them specifically.
However there is also this line "Although macrophages also attacked blood cells expressing CD47 when mice were given the antibody, the researchers found that the decrease in blood cells was short-lived; the animals turned up production of new blood cells to replace those they lost from the treatment," so this seems like a very valid concern.
However there is also this line "Although macrophages also attacked blood cells expressing CD47 when mice were given the antibody, the researchers found that the decrease in blood cells was short-lived; the animals turned up production of new blood cells to replace those they lost from the treatment," so this seems like a very valid concern.