Immunohematology Flashcards
What does the H-gene code for?
L-fucose which binds to RBC oligosaccharide side chains
(person may be HH or Hh and still produce the enzyme (L-fucosyltransferase), but hh produces no enzyme))
A gene adds ____ to L-fucose; B gene adds _____ to L-fucose.
- N-acetylgalactosamine
- D-galactose
(O gene→ oligosaccharide chain + L-fucose)
Bombay blood type
homozygous hh → no pre-cursor antigen H (L-fucose) → no A or B expression
(L-fucose allows expression of A and/or B Ags on RBC)
Bombay Blood group appears to be ____ type blood.
O type
(serum from Bombay individual will agglutinate type O cells; they have anti-A, anti-B, anti-H Abs)
Landsteiner’s Law
When sugar antigen is present on the RBC, the corresponding Ab will be absent from the serum
Blood antigens are not consistent; give 3 examples of blood antigens that change over time
- I Antigen: ⇡ w/maturity
- Lewis group: ⇣ in pregnancy
- A/B Ags: altered w/disease
Non-immune antibody
IgM: anti-A & anti-B (made w/o previous exposure)
IgM & IgG can both fix complement, but IgG must _____
have another IgG to do it; IgM only needs one
Forward typing tests for _____; Reverse typing tests for _____.
- blood group Ag (on RBCs)
- serum Ab
(must match them, forward typing = blood group Ag testing)
What does a positive Direct Coomb’s Test indicated?
patient serum has IgG Abs bound to the RBCs
(ex: erythroblastosis fetalis)
What does a positive Indirect Coomb’s Test indicate?
serum Ab
(ex: Rh- mother gets tested to see if she has anti-RhD abs that will attack an Rh+ fetus)
What is the difference between warm & cold agglutinins?
- warm: IgG, reacts at body temp (35-37 C) → cause immune response
- cold: IgM, react at temps below body temp (Ii system)
(both are Abs against blood group Ags. Warm = clinically relevant)
Warm agglutinins can cause ______.
hemolytic transfusion reactions
(prior exposure → ab production (warm agglutinin))
Agglutination is a _____ reaction
serologic
(RBCs Ag forms parrticles when coated in Abs)
In In vitro agglutination reactions, IgG are _______(always/not at all) visible w/RBC ags; IgM are _______ (always/not at all) visible
- not at all
- always
(IgGs are small and RBC are usually far apart)
Hemolysis
Ab-coating → complement activation = lysis
(pink-red supernatant from freed Hgb. This cannot be used for lab testing!)
Blood transfusion is a transplanted tissue aka, ______. The blood component is only need for a limited amount of time because _____.
- liquid allograft
- the patient’s bone marrow make up the loss
(blood does NOT have MHC I/II → safer to transplant than other tissue)
In the ABO system, structural polymorphism is the _____.
carbohydrate component of glycolipid/glycoprotein (band 3) on RBC membrane
A & B antigens (on RBCs) have structural similarities to ________.
commensal bacteria
(that is how they are made w/o exposure)
Hemolytic disease of the newborn is caused by _______.
RhD- mother has RhD+ baby → at birth, mom is sensitizes to RhD+ → antibodies will attack future RhD+ baby → hemolytic disease of the 2nd baby
hemolytic reaction is a _______ reaction to the _____.
- type II hypersensitivity
- Ag on RBC/additional sugar on cell-surface glycolipids
What is a cross-match test?
patients serum is tested before transfusion against ABO/RhD matched donors; only RBC NOT BOUND by Abs may be used otherwise → hemolytic reaction
(donor serum not tested w/patient RBC bc there isn’t enough Ab to show agglutination rxn)
AHG
anti-human globulin (IgG)
Genotype AA, AO = _____ phenotype
Genotype BB, BO = ______ phenotype
- Type A blood Ag
- Type B blood Ag
Genotype AB = _____ phenotype
Type AB blood Ag
A “secretor” is a person who secretes ______.
their blood type Ag into body fluids & secretions
(ex: saliva)
D antigen aka _____
Rh factor
D mosaic
patient has inherited some Rh+ antigen
Weak expression of D
partial Rh+ that does not react w/Anti-D antibodies (anti-Rh)
Weak D expression causes (3)
- Genetic: low density of D Ag
- Position: trans position of C gene → D gene
- Mosaic: partial D expression (absence of portion of D Ag)
Lack of Duffy antigens is associated with ______.
resistance to malaria
The Kidd System has 3 alleles, which are codominant?
- Jka
- Jkb
Rhnull results in ______
hemolytic anemia (membrane is defective→osmotic fragility)
Symptoms of Rhnull
- hemolysis
- stomatocystosis
- spherocytosis
- osmotic fragility
(they may only receive blood from other Rhnull)
P System
Patients have an anti-P antibody → fixes complement & on RBCs that are in the peripheral extremities (reduced temperature) → hemolysis when blood is warmed
(cold paroxysmal hemoglobinuria (PCH)/autoimmune hemolytic anemia)
P system is aka _____
Donath-Landsteiner antibody
Why is Ii system considered a nuisance?
Cold agglutinins encountered during lab testing & hides clinically significant antibodies which react at body temperature or with AHG
In the Kell system, there are 21 antigens. What is the clinical relevance of the Kell System?
- Anti-K (IgG) antibodies are the 2nd most antigenic ab
- associated w/HDN & transfusion reactions
(compatible blood is difficult to find for this blood group)
Kernicterus aka bilirubin encephalopathy is caused by _____
bilirubin deposits in the brain cells (>25 mg/dL)
What is RhoGAM?
Rho Immune globulin → binds to fetal RBC & removes them → mother does not make Anti-Rh Ab
(given at 30 weeks, and again 3 days after birth if baby is Rh+)
