Anti-Self Phosphatidylserine Antibodies Recognize Uninfected Erythrocytes Promoting Malarial Anemia.

Plasmodium species， the parasitic agents of malaria， invade erythrocytes to reproduce， resulting in erythrocyte loss. However， a greater loss is caused by the elimination of uninfected erythrocytes， sometimes long after infection has been cleared. Using a mouse model， we found that Plasmodium infection induces the generation of anti-self antibodies that bind to the surface of uninfected erythrocytes from infected， but not uninfected， mice. These antibodies recognize phosphatidylserine， which is exposed on the surface of a fraction of uninfected erythrocytes during malaria. We find that phosphatidylserine-exposing erythrocytes are reticulocytes expressing high levels of CD47， a "do-not-eat-me" signal， but the binding of anti-phosphatidylserine antibodies mediates their phagocytosis， contributing to anemia. In human patients with late postmalarial anemia， we found a strong inverse correlation between the levels of anti-phosphatidylserine antibodies and plasma hemoglobin， suggesting a similar role in humans. Inhibition of this pathway may be exploited for treating malarial anemia.