Warm-Reactive Autoantibodies - Investigation: Autoadsorption:
If the patient is not severely anemic and has not recently been transfused, then an autoadsorption can be performed using the patient’s own RBCs as the adsorbing cells. The advantage of using the patient’s own cells is that it guarantees that any alloantibodies to high-frequency antigens will not be inadvertently adsorbed out of the plasma along with the autoantibody.
A variety of methods are available to maximize the uptake of autoantibodies onto autologous cells, including the use of low ionic saline solution (LISS), polyethylene glycol (PEG), or pre-treatment of RBCs with proteolytic enzymes to increase the number of available autoantigen sites.
The process of adsorption is repeated several times to maximize the removal of autoantibodies, following which the adsorbed plasma is tested against a panel of reagent RBCs by indirect antiglobulin test, using the patient’s own cells as an autocontrol. One of three possible results is observed:
- Non-reactive panel: all autoantibodies have been removed from the plasma with no underlying alloantibodies identified.
- Pan-reactive panel: autoantibodies are still present and the adsorption was unsuccessful.
- Panel with specificity: all autoantibodies have been removed from the plasma and one or more alloantibody has left behind for identification.
Figure 2. Example of an autoadsorption. The autoantibody will be removed by binding the treated auto-RBC. An alloanti-e antibody is left behind in the adsorbed plasma for identification against a routine antibody panel.
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