In general, adsorption is the collection of a material on the surface of another material in a non-binding, non-permanent manner. In blood banking, adsorption refers primarily to the adherence of an antibody or antigen onto the surface of a red blood cell, described briefly below and in more detail in the linked definitions.

Adsorption is used by blood bankers to bind antibodies to red blood cells in order to remove them from the plasma and better analyze the antibodies that might remain behind. This can be done in one of two main ways: By using the patient’s own RBCs to remove autoantibodies (“autoadsorption“), or by using selected non-self RBCs to remove alloantibodies (“alloadsorption“). Autoadsorption is used most often in the workup of warm autoantibodies, to remove autoantibodies so that underlying (“masked”) alloantibodies may be identified. Alloadsorption may be used in complicated antibody identification workups, typically where there is more than one antibody present. In either setting, the idea is to get certain antibodies “out of the way” so that the antibody or antibodies “left behind” in the sample after the adsorption may be analyzed (the serum that is left behind is called “adsorbed serum“).

In addition, certain plasma antigens can passively bind (adsorb”) to the surface of the red cell in a non-permanent way; the most famous of these are Lewis System antigens (for more, see my 2013 Lewis System video).

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