Blood Group Compatibility Flashcards
Who discovered ABO blood groups ?
Karl Landsteiner in 1901
How were ABO blood groups discovered?
Discovered based on agglutination reactions between one persons blood and another
blood transfusion between individuals of different blood groups led to red cell destruction. This did not occur between individuals of the same blood group.
When was the first successful blood transfusion performed?
at the Mount Sinai Hospital in NY in 1907
ABO antigens are what type of antigens?
carbohydrate antigens
What gene codes for the O or H antigen backbone?
Fucosyl transferase 1 (FUT1)
What does glycosyltransferase A or GTA gene code for
N-acetylgalactosamine or the A antigen being added
What is the B antigen? what gene codes for it?
galactose
coded for by glycosyltransferase B
What results in O blood group?
lack of both GTA and GTB
What kind of expression is there with the GTA and GTB genes?
co-dominant expression
What is the Bombay phenotype?
a mutation in FUT1 results in a defective H antigen so they are automatically O phenotype regardless of the GTA/GTB genotype
How do people develop antibodies against the A/B/or both antigens that they themselves do not have?
Due to exposure to similar carbohydrates on gut bacteria
- mostly IgM but some IgA and IgG
When do infants develop anti AB antigens?
only between 6-12 months of age
What happens during an acute hemolytic transfusion reaction?
Rapid intravascular destruction of transfused RBCs by preformed antibody
What kind of preformed antibodies against RBCs exist? what do they do?
IgM class that fix complement
What happens following fixation of complement by IgM antibodies?
Intravascular hemolysis, release of free hemoglobin and pro-inflammatory cytokines
What are some symptoms of an acute hemolytic transfusion reaction?
- DIC
- Hypotension/Shock
- Acute renal failure
What is the mechanism for a hyperacute rejection reaction?
- Preformed antibodies bind to the A and or B antigens on the endothelial cells of the vasculature of the transplanted organ
- Antibodies activate the classical complement pathway
- products of complement and antibodies activate neutrophils
- Neutrophils degranulate and release lytic enzyme that damage the endothelium and expose the vessel wall
- MAC damages the endothelium
- platelets adhere to the vessel wall and form a clot (thrombosis) which blocks circulation
What are Rh antigens?
Glycoproteins expressed on RBCs
Where are the coding genes located for Rh antigens ? What gene
on chromosome 1
RHD
Explain the difference between RHD, RHCE and what the D antigen is
RHD gene codes for RhD or the D antigen
Lack of D antigen is referred to as d
RhD (D antigen) colloquially referred to as Rh
RHCE makes RHCE protein that comes in 4 variants:CE, Ce, cE and ce
RhD inheritance is…
dominant
What is erythroblastosis fetalis caused by
incompatibility between maternal and fetal blood antigens
What is the most common cause of erythroblastosis fetalis?
RhD incompatibility where the mother is Rh- and the fetus if Rh+
What happens if fetal Rh+ blood cells cross the placenta into the Rh- mother?
Mother develops anti-Rh antibody which then crosses the placenta
What happens when anti Rh antibodies cross the placenta back into the Rh+ infant?
- Fetus develops anemia
- Fetus can die due to heart failure (hydrops fetalis)
- Newborn can develop anemia and jaundice because the liver cannot clear the bilirubin
- seizure and brain damage
What can be done to prevent erythroblastosis fetalis?
- Test mothers early in pregnancy for Rh
2. If mother is Rh-, give her a rhogam
What is a Rhogam ? when is it given?
anti-RhD immunoglobulin
given at 28 weeks gestation, time of delivery, or time of any trauma/bleeding
What does the Rhogam do?
Masks the D antigen on fetal cells and prevents maternal sensitization
What treatment can be given for an anemic fetus?
direct blood transfusion
What is the hemoglobin level at which you would want to transfuse blood for a stable patient?
70-80 g/L
When do you transfuse plasma? When do you often also need to give this to patients?
When people need a massive transfusion
Often also give to patients on Warfarin therapy because they lack a lot of clotting factors that are found in plasma
What is the Buffy coat (B1) method?
Way of manufacturing blood products
- Add anticoagulant
- Rapid cool and centrifugation
- Remove plasma unit and the platelets (stay stuck on buffy coat bag)
- Filter out leukocytes
Why do you need to have a leukoreduction stage?
because as they die, the leukocytes will burst and release their cytokine products
How do you manufacture platelets?
- Take a plasma unit from a male donor
- Filter it though 4 bufy coat bags in sequence
- Centrifuge and extract RBCs, filter out leukocytes
What are 7 possible transfusion reactions that can occur?
- Allergic/anaphylactic reactions
- Febrile or non-hemolytic from contaminating donor leukocytes and cytokines
- Transfusion-associated cardiac overload (TACO) from transfusing too fast
- Transfusion related acute lung injury (TRALI) due to antibodies to HLA
- Autoimmune cellular destruction
- hemolysis (acute or delayed)
- Neutropenia - Infection
- Serological (anti HLA or Rh antibodies)
What is the purpose of the diversion pouch when collecting blood?
to get rid of the skin plug which can have contaminating bacteria on it
What is the most fatal transfusion reaction? Which one causes the most deaths/is more common?
TRALI is the most fatal
TACO causes the most deaths
What is compatibility like for plasma transfusion? Why?
the opposite of what it is for blood transfusion..
ex: O can get blood from anyone but AB can only get blood from AB
B can get plasma from B or AB
A can get from A or AB
Because there will be antigens in the plasma from where you are transfusing
Who is the universal plasma donor?
AB
Can donors with anti Rh antibodies be used for donations? Which kinds?
they cant be used for red cells, platelets or plasma production
For platelets, what is the compatibility testing/administration like? Why
Try to transfuse ABO matched platelets if available. Otherwise:
- Possibility of a hemolytic reaction (eg. Group A recipient receives group O platelets, group O platelets contain anti-A antibodies in plasma).
- Possibility of donor platelet destruction (group O recipient receives group A platelets, low levels of A antigen expressed on platelets).
What is forward typing looking for?
- Is A or B antigen present on the patients cells
2. Is D antigen present on the patients cells
What is reverse typing looking for?
If there are any anti-A or anti-B antibodies present in the patients serum
How does forward typing work?
Add the patients blood and anti A, B and Rh antibodies
If there was a crossreacting Ab on the RBC, it will not pass though the gel and will therefore stay at the top
How does reverse typing work?
Add the patients serum with either A or B cells
if there is agglutination, it means that they form antibodies against one or both of those blood types
- ie cant be their own
What screening test is analogous to reverse typing
Indirect antiglobulin test (IAT)
What is the purpose of the IAT test?
To see if the patient has antibodies against the antigens present on the allogeneic screen red blood cells
What is done for an IAT screen?
- Patient serum
- Group O red cells of known antigenic profile
- All clinically significant antigens have to be expressed among the screening red cells
What is a crossmatch test?
like an IAT screen
• Patient serum is used
• Donor red cells are used
Gives you a either a positive or negative result
What are the most common antigens causing delayed hemolytic transfusion reactions?
RHD, RHCE or Kidd
What is the usual presentation of helayed hemolytic transfusion reactions?
Milder presentation of anemia and low grade fever
What is happening during a delayed hemolytic transfusion reaction? what kind of antibody responses
- Primary antibody response to a red cell alloantigen on recently transfused red blood cells.
- Secondary antibody response to a blood group antigen that was previously encountered during pregnancy or transfusion.
What is DAT?
direct antiglobulin test
What does a DAT do?
checks for antibody bound to red cells in a patient
What is the reagent for a DAT test?
• Poly-specific anti-human globulin reagent
- Anti-IgG and anti-C3d
