Antibody elution
An antibody elution is a
Antibody elutions are specialized tests used in clinical blood banks. Examples of routine tests include ABO/Rh, antibody screen, antibody identification, and antiglobulin testing. Examples of other specialized tests used in blood banking include: treatment with thiol reagent, monocyte monolayer assay, enzyme treatment, and adsorptions.[2]
This procedure aids in the investigation of antibodies that are difficult to identify, distinguishing
Background
Blood group systems
Red blood cell membranes consist of a
As of 2023, there are 44 blood group systems, each containing several red blood cell antigens totaling 354, determined by approximately 49 separate genes.[7] Of these antigens, only a handful are considered clinically significant, meaning that they can stimulate the production of antibodies capable of causing red cell hemolysis. This is particularly important for the transfusion of packed red blood cells and other cellular blood products. Examples of blood group systems that contain antigens capable of inducing clinically significant alloantibodies (antibodies against non-self antigens) include, but are not limited to the ABO, Rh, Kell, Duffy, Kidd, and MNS blood group systems.[8]
Antibody identification
Antibodies to blood group system antigens and their characteristics must be identified when such antibodies are detected in a potential recipient's serum or plasma.[9] The specificity of the antibody aids the medical laboratory scientist in determining if the antibody is clinically significant. Antibody identification is a very laborious process.[1]
Characteristics of clinically significant antibodies include: reactive at body temperature (37°C),
The presence of
Methods of antibody elution
There are several methods of antibody elution used in clinical blood banking. Some of these methods include manipulating temperature, manipulating pH, use of organic solvents, and chloroquine.[2] Each of these methods have advantages and disadvantages, and the method of elution will vary depending on clinical utility. One of the more commonly used methods is an acid elution, because it is quick, cheap, and relatively easy to perform.[3][12]
Acid elution principle
The main steps involved in an acid elution include:[3][2]
- Separate and thoroughly wash red blood cells from a peripherally collected EDTA blood collection tube using centrifugation.
- Mix washed patient red blood cells, that are positive for the IgG phase of the direct antiglobulin test, with glycine acid (pH 3.0).
- Centrifuge the mixture, and immediately remove the supernatant from the destroyed red blood cells.
- Add buffer to return the mixture to a neutral pH. This step is critical for further antibody identification testing, because the antibody will not react at a pH of less than 7.0.
- Additional centrifugation may be needed to clarify the solution.
- The resulting solution is known as the eluate. This eluate is then tested against a panel of red blood cells with known antigen profiles. This antibody identification procedure will aid in determining the specificity of the antibody.
Determining when to perform an antibody elution
Antiglobulin testing
The main method of antibody and antigen detection used in a clinical laboratory is red blood cell agglutination.[1] Most IgM antibodies are easier to detect because they are larger and react at room temperature (20°C).[13][14] This concept is what makes ABO/Rh testing so quick and easy to perform. However, most clinically significant non-ABO antibodies react at body temperature (37°C) and will not result in agglutination without the addition of multiple steps: incubation, washing, and the addition of anti-human globulin (AHG) reagent.[15]
Anti-human globulin is an antibody directed against human IgG antibodies.[16] When the smaller IgG antibody is attached to red blood cells, the larger AHG antibodies create a cross-link between IgG sensitized RBC forming visual agglutination. When this agglutination is observed, the antiglobulin test is considered positive for the detection of the antibody and/or antigen(s) present.[2]
There are two main types of antiglobulin testing: indirect and direct.[17][18] Indirect antiglobulin testing is used to detect antibodies in plasma/serum, whereas direct antiglobulin testing is used to detect antibody bound to red blood cells. When the direct antiglobulin test is positive, we must perform an antibody elution to remove the antibody for identification and to determine the antibody's clinical significance.[3]
See also
References
- ^ OCLC 1048659017.)
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: CS1 maint: location missing publisher (link) CS1 maint: others (link - ^ OCLC 1163631267.)
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: CS1 maint: location missing publisher (link) CS1 maint: others (link - ^ OCLC 1336509285.)
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: CS1 maint: location missing publisher (link - ^ "Glossary: Elution - Blood Bank Guy Glossary". Blood Bank Guy. Retrieved 2023-04-17.
- PMID 25099803.
- OCLC 1200832451.)
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: CS1 maint: location missing publisher (link - ^ ISBT. "Red Cell Immunogenetics and Blood Group Terminology | ISBT Working Party". www.isbtweb.org. Retrieved 2023-04-10.
- ^ "Clinically Significant Red Cell Antibodies". Bloodworks Northwest. Retrieved 2023-04-10.
- OCLC 1162875932.
- S2CID 78254504.
- ^ "Glossary: Autoantibody - Blood Bank Guy Glossary". Blood Bank Guy. Retrieved 2023-04-17.
- ^ "Glossary: Elution - Blood Bank Guy Glossary". Blood Bank Guy. Retrieved 2023-04-17.
- ^ "Glossary: IgM". Blood Bank Guy. Retrieved 2023-04-20.
- ^ "Glossary: IgG". Blood Bank Guy. Retrieved 2023-04-20.
- OCLC 817741300.
- ^ "Glossary: AHG Phase - Blood Bank Guy Glossary". Blood Bank Guy. Retrieved 2023-04-20.
- ^ "Glossary: Direct Antiglobulin Test - Blood Bank Guy Glossary". Blood Bank Guy. Retrieved 2023-04-20.
- ^ "Glossary: Indirect Antiglobulin Test". Blood Bank Guy. Retrieved 2023-04-20.