Human red cell antigens rare cases of hemolytic disease of the newborn, however. Human red cell antigens In addition to the defined human blood group systems, there are erythrocyte antigens which do not meet the definition of a blood group system. Most of these are either nearly universal in human blood or extremely rare and are rarely significant in a clinical setting. Reagents to test for these antigens are difficult to find and many cannot be purchased commercially. These three groups are antigens with shared characteristics but do not meet the International Society of Blood Transfusion (ISBT) definition of a human blood group system.
Red blood cell among the bilayer is the result of the function of several energy-dependent and energy-independent phospholipid transport proteins. Proteins called “Flippases” move phospholipids from the outer to the inner monolayer, while others called “floppases” do the opposite operation, against a concentration gradient in an energy dependent manner. Additionally, there are also “scramblase” proteins that move phospholipids in both directions at the same time, down their concentration gradients in an energy independent manner. There is still considerable debate ongoing regarding the identity of these membrane maintenance proteins in the red cell membrane. The maintenance of an asymmetric phospholipid distribution in the bilayer