White blood cells found to play key role in controlling red blood cell levels

Researchers at Albert Einstein College of Medicine of Yeshiva University and the Icahn School of Medicine at Mount Sinai have found that macrophages - white blood cells that play a key role in the immune response - also help to both produce and eliminate the body's red blood cells .

http://www.eurekalert.org/pub_releases/2013-03/aeco-wbc031413.php