ABO and Rhesus Blood Groups Overview

This flashcard set covers the essentials of the ABO and Rhesus blood group systems, including their discovery, genetics, biochemistry, and clinical implications in blood transfusions and pregnancy.

Karl Landsteiner

The scientist who discovered in $1900–1901$ that mixing red blood cells and serum from different individuals could cause agglutination, leading to the classification of blood groups A, B, and O.

Agglutinogens

The variety of blood group antigens found on the cell membranes of human red blood cells that can trigger antigen–antibody reactions.

H Antigen

A common carbohydrate precursor molecule located on red blood cells, platelets, and other cells, upon which ABO antigens are built.

Transferase Enzymes

Two different types of enzymes that modify the H antigen into distinct ABO molecules by adding different terminal sugars.

Chromosome 9

The specific chromosome that contains the genetic locus responsible for determining an individual's blood group alleles (A, B, and O).

Codominant

The genetic relationship between A and B alleles in the ABO system, where both are expressed phenotypically when present together.

Agglutinins

Antibodies produced in the plasma against red cell antigens that are not present in an individual's own cells.

IgM

The predominant class of ABO antibodies that infants develop against foreign antigens; these do not cross the placenta.

Rhesus (Rh) Blood Group System

The second most important blood group system, discovered in $1940$, composed primarily of C, D, and E antigens.

D Antigen

The most clinically relevant Rh antigen; its presence on the red cell membrane classifies an individual as Rh positive.

Blood Compatibility

The clinical condition where blood of a similar group is given to an individual to prevent dangerous antigen-antibody reactions.

Hemolysis

The process where red blood cells clump and rupture, liberating free hemoglobin into the plasma, often due to a transfusion reaction.

Universal Donor

Individuals with type O blood who can give blood to any type because their red cells lack A and B antigens, preventing antibody reactions.

Universal Recipient

Individuals with type AB blood who can receive any blood type because they have no circulating anti-A or anti-B agglutinins.

Cross-matching

The procedure of mixing donor red cells with recipient plasma on a slide to check for agglutination before a blood transfusion is performed.

Erythroblastosis Fetalis

A hemolytic disease of the newborn that occurs when maternal anti-Rh antibodies cross the placenta and destroy the red blood cells of an Rh-positive fetus.

Hydrops Fetalis

A severe form of hemolytic disease in a fetus characterized by anemia, severe jaundice, and edema.

Anti-D Immunoglobulin

A treatment given to Rh-negative mothers within $72$ hours postpartum or after procedures to prevent the formation of anti-RhD antibodies.