Week 2 Flashcards
A molecular structure, associated with a cell membrane, that may illicit an immune response.
• Found on viruses, bacteria, fungi, protozoa, blood cells, organs and tissues.
Antigen
Glycoprotein that recognises a particular
epitope on an antigen and facilitates clearance of that antigen.
Antibody (Immunoglobulin):
What genes at three separate loci control the occurrence and location of ABO antigens on
cells and in secretions?
H gene, ABO genes, Se (Secretor) gene
A gene that has no detectable product or phenotypic effect is called a _________
Amorph
List the alleles for each of the following genes
H gene, ABO genes, Se (Secretor) gene
- H and h alleles (h is an amorph)
- A, B and O alleles (O is an amorph)
- Se and se alleles (se is an amorph)
H antigens are an indirect product are the foundation for which antigens?
Foundation for A and B antigens
A common structure for A,B and H antigens is an ________________ chain
oligosaccharide
H allele codes for a transferase enzyme that adds a sugar (fucose) to the terminal sugar of the oligosaccharide chain which makes a ____________
H antigen
“A” gene codes for a transferase enzyme
that adds ______________ to the terminal sugar of H antigen.
N-acetylgalactosamine
“B” gene codes for a transferase enzyme that adds__________ to the terminal sugar of the H antigen
D-galactose
Which alleles are co-dominant and which is silent
A and B alleles are co-dominant , O allele is silent
Soluble antigens (A, B, and H) can be found in the secretions of some individuals. • This is controlled by the ________ genes
H and Se
Which genotypes are secretors and which genotypes are non secretors?
SeSe and Sese are secretors - 80% of the population.
sese are non secretors. se is an amorph nothing is expressed.
ABO subgroups differ in amount of …..
antigen present on the RBC membrane
What are the two major subgroups of A
A1 and A2
• A1 - ~80% of group A or AB individuals
• A2 - ~20% are A2 or A2B
What’s the difference between A1 and A2 Antigens? (2)
Quantitative difference
Difference in carbohydrate composition
Can A2 develop anti-A1 antibodies?
Yes
Why is the A2 phenotype important?
A2 and A2B individuals may produce an anti-A1 causing an incompatibility crossmatch
What is the Bombay phenotype?
(Oh) it’s an Inheritance of hh the h gene is an amorph With no H Ag’s, cannot make A or B Antigens
Does the Bombay serum have strong anti-A, anti-B and anti-H?
Yes
The Bombay RBC’s appear to be what blood type? and what agglutinates with the serum?
Appears to be O and it agglutinates ALL ABO blood groups even O.
What ABO groups could you transfuse Bombay phenotype blood to?
Can transfuse Bombay phenotype to anyone
What ABO blood group could you transfuse to patient with Bombay group?
Individuals with Bombay phenotype can only receive blood from a Bombay phenotype.
Only blood group system where antibodies are present in individuals with no known exposure to blood or blood products
ABO blood group system
Transfusion of incompatible group may result in __________
immediate lysis of donor RBC
Can newborns passively acquire maternal antibodies?
Yes. IgG can cross the placenta
The Anti-B produced by group A individuals and the Anti-A produced by group B individuals is predominantly _______
IgM
The Anti-A, Anti-B and Anti-A,B produced by group O individuals is predominantly________
IgG (with some IgM)
Which blood groups contain anti-A in their serum
Group O and B
Anti-A can be separated into what 2 different components?
Anti-A and Anti-A1
Anti - A1 Clinically Significant? Abs Class? Thermal range? HDNB? Extravascular or Intravascular Transfusion reaction?
Clinically Significant? - Sometimes
Abs Class? IgM
Thermal range? 4 - 22
HDNB? No because IgM cannot pass the placenta
Extravascular or Intravascular Transfusion reaction? - Rarely intravascular
Anti-AB is found in serum of which blood group?
Group O individuals
Anti-A, Anti-B, Anti-AB Clinically Significant? Abs class Thermal range HDNB Transfusion reaction?
Clinically Significant? - Yes Abs class - IgM, IgG Thermal range - 4-37 HDNB - Yes Transfusion reaction? Yes both Extravascular and Intravascular
Rh is the most complex system with over 50 Rh antigens described. What are the 5 principal antigens?
– D, C, c, E, e
Rh antigens are _________
proteins
What is the current inheritance theory:
2 loci on the short arm of Chromosome 1
What are the 2 naming systems developed before advances in molecular genetics
- Fisher-Race
* Wiener
What are the additional systems developed so universal language available for use with computers
- Rosenfield
* ISBT
Fisher-Race terminology looks like ______
Wiener terminology looks like ________
Fisher - CDE, cde
Wiener - r’, R1
When there is no Rh antigens present on the RBC membrane what can be seen on a blood film and why?
Stomatocytosis because Rh antigens are integral part of RBC membrane, absence leads to loss of membrane
integrity. mild hemolytic anaemia
What test do Rh antibodies agglutinate in?
IAT
Rh antibodies: Clinically Significant? Abs class Thermal range HDNB Transfusion reaction?
Clinically Significant? Yes Abs class - IgG Thermal range - 4-37 HDNB - Yes Transfusion reaction? Only Extravascular not Intravascular
After ABO, the Rh system is the second most important system, why?
D antigen is extremely immunogenic. If D neg patients are exposed to D antigen they will most likely make Anti-D antibody.
Will individuals produce antibodies to ABO antigens they do not possess or that they do possess?
Do not posses
For a Forward group – tile or slide what do you need to add?
Anti-serum: Anti-A, Anti-B, Anti-D + the patients red cells
For the Reverse Group what do you add?
Patient plasma + commercial red cells A1, B
Most ABO discrepancies are ______ in nature and can be resolved by doing what 3 things?
Technical
- Correctly repeating the test
- Carefully checking reagents
- Careful reading and recording of results
Give 2 examples of ABO discrepancies that are antibody related.
- New born infants, elderly patients
- Patients with lymphoma.
- Patients using immunosuppressive drugs e.g BM transplant
- Patients with immunodeficiency disease
Give 2 examples of ABO discrepancies - Antigen related
Can be seen in patients with leukaemia and Hodgkin’s disease and some bacterial infections
What are some ABO discrepancies - Serum related
Elevated levels of globulin lead to rouleaux formation
• Multiple myeloma
• Hodgkin’s lymphoma
(to resolve wash patients red cells in saline)
List some steps as a scientist that you would do to resolve a ABO discrepancies
- check patient diagnosis and transfusion history
- check for technical errors
- have a second scientist repeat the test
- incubate patients serum for 15min at room temp
When D antigen is weakly expressed, detection requires what test?
indirect antiglobulin testing (IAT) • Incubate cells with Anti-D antisera • Wash • Perform antiglobulin test to detect presence of Ig bound to cells • Cannot be done if cells at DAT +ve
