Blood Groups And Transufuions Flashcards
Antigens =
Cell surface molecules usually a protein that causes an immune response
How are A,B,O antigens inherited?
In a Medelian pattern, 1 allele from mum, 1 from dad. A, B alleles are co-dominant.
A codes for an enzyme that adds A antigens to surface
B codes for an enzyme that adds B antigens to the surface
O does not code for an enzyme
What is the H allele?
Before A or B antigens can be added to the surface. A gene that codes for the formation of a chain has to be present.
Usually present, but of not then A or B antigens wont be added. Blood known as Bombay blood.
Why do we have AB antibodies
Theories that they developed against environmental antigens.
Infants < 3 months will produce no antibodies
Rhesus antigens overview:
There are 45 different Rh antigens
It’s genetic locus is on
chromosome 1
2 genes
RHD codes for RHD And the second RHCE codes for RhC and RhE.
They are highly immunogenicity - antibodies against RhD in those without it commonly found.
Can cause haemolytic transfusion reactions and haemolytic disease in a foetus.
Rhesus positive also known as
Rh D
What is HDFN - haemolytic disease of newborn?
Rh D sensitisation most common cause:
Rh positive father, Rh negative mother
Rh negative mother ends up with an Rh-positive baby.
Baby’s blood will enter mothers causing production of Rh antibodies.
These Rh antibodies remind in mothers blood stream.
Second child Rh positive antibodies attack baby’s blood cells causing Rh disease.
How to perform ABO and Rh D grouping?
Forward typing vs reverse typing…
Forward typing - patients RBC’s are added to antibody A and then to Antibody B and Antibody RhD
If antibody finds corresponding antigen it will clot the blood.
Reverse typing - patient plasma is added is added to A blood, B blood and RhD
If antibodies present then it will clot with the antigens added to the tubes.
If a clot does form, it will sink to the bottom
