But a small percentage of people — including Zainab — produce antibodies in the presence or absence of certain antigens, prompting the body to reject the blood. But those people still get into accidents or come down with diseases like everyone else, so there's a network of blood centers that specialize in rare blood, keeping a database of scarce combinations of antibodies and shuttling it across the country to patients in need.

Source: Los Angeles Times December 05, 2018 17:26 UTC