Blood groups and transfusions Flashcards
Charcateristics about IgM
-Naturally occurring and present in new born too, against group A or group B antigens.
-Present as a pentamer with a J chain in the middle
-Helps in agglutination and activation of complement and membrane attack complex.
-Rapidly breakdown of foreign RBCs
-Involved in antibodies against ABO and RhD blood groups;
Charcteristics of IgG
-Present mainly during after transfusions and foeto-maternal transmissions.
-Present as individual antibodies.
-Agglutinates foreign RBCs and takes them to cplenic macrophages by binding its Fc to the macrophage triggering phagocytosis of the whole complex.
-Present mostly in the liver and the spleen.
What are the names and location of the genes involved in the ABO system.
-FUT 1 and FUT2 genes code for H substance.In chromosome 19
-A and B genes found in chromosome 9. Code for glucosyl transferase to make A and B antigens.
How are the different red cells antigens poduced?
O antigen.- original form. 5 sugars and a lipid tail
A antigen- another N-acetylgalactosamine monomer added to the original form.
B antigen- another galactose monomer added to the original form.
What are the combinations of antigen and antibodies against antigen that a person can have?
Person with O antigen has anti-A and anti-B.
Person with A antigen has anti-B.
Person with B antigen has anti-A.
Person with AB has no antibodies against ABO.
What 3 plasma components can we use for a transfusion?
Name their shelf life
Plasma reduced cells: shelf life 35 days
Pooled platelet concentrate: shelf life of 5 to 7 days.
Frozen plasma (at -40 degrees): shelf life of 2 years.
Describe the process to determine the blood group of a person from their blood sample.
-Micro titre gels tubes, each containing antibodies against each blood group in the gel.
-Blood sample added in each tube and they are all centrifuged.
-If there is red cells are high up in the gel: they are are agglutinated by the antibody.
-If the red cells sink to the bottom of the tube, then they aren’t agglutinated, meaning antibody doesn’t affect them. Same with RhD test.
-Example: if red cells sink to the bottom in tube containing anti-B, then patient is type A.
What antigens are involved in the rhesus system and where are their genes located?
Antigens c,C,D,e and E. Their genes are found in chromosome 1 and their inherited as triplets from each parent.
What occurs during the haemolytic disease of a new born?
-Fetal RBC containing father’s antigens enters mother’s circulation, triggering an immune response.
-IgG secreted, which can cross the placenta and attack fetal cells
-This causes anemia, jaundice,brain damage and even fetal death.
List the ways to prevent RhD immunisation
-Anti-D negative prophylaxis: given at 28 weeks, after delivery and during obstretics events.
-Kleihauden test: to test if fetal RBCs in mother. By acid elusion test. Fetal Hb is more resistant to dilution so it will appear more red than mother’s in the blood film.
-Foetal monitoring.
-Neonatal management.
Explain foetal monitoring
-Flow in cerebral artery
-Liver and spleen size
-Ascites- fluid accumulation in the abdomen
All of these done by ultrasound or by umbilical cord sampling.
-Blood tests and transfusions can be done from umbilical vein
Explain neonatal management
-Allowing antibodies to decline
-Phototherapy to break down bilirubin
-Clinical assessment
-Blood count and concentration of reticulocytes, RBC, bilirubin. antibodies, blood group
-Direct Coombs test: to detect membrane-bound antibodies
-Top-up or exchange transfusion.
What reactions can a person have to receiving a blood transfusion?
-Acute haemolytic reaction
-Delayed haemolytic reaction
-Urticaria/anaphylaxis
-Fever
Describe possible reasons for failures in transfusion
Failure in identifying donor
Incorrect labeling of donor/patient group
Lab errors: Abs not working, wrong sample
Failure in identifying recipient
