Antibody (Isohaemagglutinin)
Definition
An immunoglobulin in plasma directed against red-cell antigens the host does not carry. Group O serum carries anti-A and anti-B; group AB serum carries neither.
- Also called
- Naturally occurring anti-A and anti-B antibodies
- Group O serum
- Carries anti-A and anti-B
- Group AB serum
- Carries neither anti-A nor anti-B
- Forensic use
- Reverse (serum) typing to confirm ABO group
Common questions
Why are isohaemagglutinins present without prior exposure to foreign blood?+
They arise naturally in early infancy, thought to develop from immune responses to A- and B-like antigens on common bacteria and food, so a person's serum reliably carries antibodies against whichever ABO antigens their own red cells lack.
How does testing for isohaemagglutinins support ABO grouping of a stain?+
Reverse typing checks the serum component against known A and B cells to cross-check the forward typing result from the red cells, and agreement between the two methods increases confidence in the reported blood group from a degraded or mixed stain.
Related terms
- ABO System
- The blood-group classification described by Karl Landsteiner in 1901: groups A, B, AB, and O, defined by antigens on red-cell surfaces and...
- Agglutination
- Clumping of red cells that occurs when antibodies in serum bind to incompatible antigens on the cell surface, cross-linking cells into visible...
- Antigen
- A molecule recognised by the adaptive immune system through specific binding to an antibody or T-cell receptor. Defined by immunogenicity (capacity to...
- Bombay Phenotype (Oh, Hh)
- Y. M. Bhende, 1952, K.E.M. Hospital Mumbai. Homozygous absence of the H antigen, so neither A nor B can be expressed; types...
- ISBT
- International Society of Blood Transfusion. The authority that catalogues and numbers the 35+ recognised blood group systems.
- MNS System
- A blood group system comprising M and N antigens on glycophorin A (GYPA) and S and s antigens on glycophorin B (GYPB)....
- Rh System
- A blood group system defined by antigens on two proteins encoded by the RHD and RHCE genes on chromosome 1. The clinically...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...