Hemagglutination
Definition
Agglutination specifically involving red blood cells as the antigen-bearing particles. Direct hemagglutination occurs when antibodies bind surface antigens naturally present on red cell membranes, as in ABO typing. It is distinguished from indirect hemagglutination, where red cells are coated with exogenous antigens.
- Definition
- Agglutination of red blood cells as antigen carriers
- Direct type
- Antibody binds native red cell surface antigens
- Example
- ABO blood typing
- Contrast
- Indirect: cells coated with exogenous antigen
Common questions
How does direct hemagglutination confirm a person's ABO blood type?+
Anti-A and anti-B reagent antibodies are mixed separately with a blood sample; visible clumping in a given reagent shows the corresponding antigen is present, and the pattern of which reagents clump identifies the blood type.
Why would a forensic laboratory use indirect rather than direct hemagglutination?+
Indirect hemagglutination lets examiners detect antibodies or antigens that red cells do not naturally carry, by first coating the cells with a chosen antigen, extending the technique beyond native blood-group markers.
Related terms
- Agglutination Titre
- The reciprocal of the highest dilution of a serum or antigen solution at which visible agglutination still occurs. A titre of 1:64...
- Antiglobulin (Coombs) Test
- A two-stage assay that detects IgG antibodies bound to red blood cells. The direct test detects in-vivo cell-bound IgG; the indirect test...
- Low-Ionic-Strength Saline (LISS)
- A reaction medium with reduced salt concentration used to enhance agglutination sensitivity, particularly for IgG antibodies. Lowering ionic strength reduces the electrostatic...
- Passive (Indirect) Agglutination
- An agglutination format in which a soluble antigen or antibody is adsorbed or covalently linked to a carrier particle (latex bead, tanned...
- Prozone (Hook) Effect
- A false-negative agglutination result caused by antibody excess. When antibody molecules outnumber antigen sites, each site is occupied by a single antibody...