Role of CD47 as a marker of self on red blood cells

The immune system recognizes invaders as foreign because they express deter minants that are absent on host cells or because they lack "markers of self " that are normally present. Here we show that CD47 (integrin-associated pr otein) functions as a marker of self on murine red blood cells. Red blood c ells that lacked CD47 were rapidly cleared from the bloodstream by splenic red pulp macrophages,CD47 on normal rea blood,cells prevented this eliminat ion by binding to the inhibitory receptor signal regulatory protein alpha ( SIRP alpha). Thus, macrophages may use a number of nonspecific activating r eceptors and rely on the presence or absence of CD47 to distinguish self fr om foreign. CD47-SIRP alpha may represent a potential pathway for the contr ol of hemolytic anemia.