ABO and Rh systems Flashcards
How are antigens attached to RBC?
By either carbs to lipids, carbs to proteins or by proteins
How many recognised antigens are there?
Over 300, majority not clinically significant
Antigens are attached to carrier molecules, what other functions do carrier molecules have? (7 functions)
Contribute to the membrane structure integrity, they act as protein transporters by producing pores in the cell membrane, act as receptors for extracellular ligands, they act as adhesion proteins by allowing red cells to stick to things, act as extracellular enzymes, complement regulatory proteins, act as maintainers of surface charge in the glycocalyx
Which are the carb based blood systems?
ABO, Lewis, P and Li
Which are the protein-based systems
Rh, Kidd, Kell, Duffy, Lutheran and MNS
When is antibody production started?
At a very early age, because sugars we come in contact with are identical to or very similar to the ABO system, blood group antigens are found throughout nature, it is called molecular mimicry
What do T-regulatory cells do?
They constantly search for antibodies that may harm our own red cells
What does an allele code for?
Codes for an enzyme that makes antigens and allows attachment of the A antigen
What is a H antigen?
It is a carb structure, specifically, L-fructose that is bound to precursor chains on the red cell surface, without it A and B carbs cannot attach to the RBC membrane
What enzymes allow the attachment of A and B to the H antigen?
A allele codes for N-acetyl-galactosaminyl transferase
B allele codes for D-galactosyl transferase
How is the H antigen attached to the red cell membrane?
It requires the activity of enzymes FUT-1 and FUT-2. There are 2 types of precursor chains that h antigen can attach to, type-1 and type-2. Type-1 chains are found in secretions, primarily glycoproteins and are beta 1-3 linkage, while type-2 chains are found on the cell surface, primarily glycolipids and are beta 1-4 linkage
What are the two types of H antigen connections?
Type 1 - FUT-2 uses type 2 enzyme on type 1 chain, L-fructose is added to complete connection
Type 2 - FUT-1 uses type 1 enzyme on type 2 chain, fructose is added to complete connection
What is an individual with Bombay phenotype?
The individual has the inability to make type 2 H antigen due to a mutation with FUT-1 causing A and B antigen not being expressed. This causes the patient to appear as group O blood type, but they will still have A, B and H antigen in their blood meaning they can only receive blood from people with the same condition
Can a mutation in the FUT-2 gene occur?
Yes, it is common in 20-30% of people and causes the inability to produce type-1 H antigens, but it doesn’t cause a problem in the person
How many sub-groups of blood type A are there?
5, A1, A2, A3, Ax and Ael. More than 99% of people are either A1 or A2. A2 is less efficient than A1 at attaching the A antigen, meaning that RBC have 20-25% less A antigen that A1 cells, this can sometimes result in weak agglutination reactions
