Unit 3: The ABO and Rh Flashcards
Who discovered the ABO blood system and when?
1902 Karl Landsteiner
What age do you see naturally occurring antibodies to the ABO antigens they lack?
people older than 3-6 months of age
What did Landsteiner demonstrate?
a person’s serum contains naturally occurring antibodies to an antigen you don’t have
What are the Landsteiner rules?
If the ABO antigen is present on the cells, the corresponding antibody will be absent in serum
If the ABO antibody is present in the serum, the corresponding antigen will be absent on the cells
If you have B or A antigen present, what do you lack?
antibody B or A
Blood type O has no ___ but _____
antigen A or B but both antibodies A and B
Blood type AB has what antigens/antibodies present?
Both antigens A and B but no antibodies
Incompatible ABO transfusion results to…
acute intravascular hemolysis
renal failure
fatality
ABO reagents made from ___ are not often used due to problems with nonspecificity
human serum
ABO typing reagents are made from….
monoclonal antibodies
What are the lectins used in blood banking?
Dolichos biflorus (A1 or A1B cells) Bandeiraea simplicifolia (B cells) Ulex europaeus (O cells, H specificity)
What are the ABO reagent colors?
Anti-A is blue
Anti-B is yellow
Anti-A1B & Anti-H are colorless
What does forward typing test for?
antigens (patient RBCs) using antisera
What does reverse typing test for?
antibodies (patient serum) with reagent RBCs
What is antisera?
reagents with known ABO antibodies
What is the least common ABO phenotype?
AB
What is the most common ABO phenotype?
O
What antibody class is IgG only?
Anti-A,B
Which population has the highest frequency of O blood phenotype?
Hispanics
Which population has the highest frequency of A blood phenotype?
Caucasians
Which population has the highest frequency of B blood phenotype?
African Americans
Which population has the highest frequency of AB blood phenotype?
Asians
When do antibody productions peak?
5-10 years of age
What is antibody A,B?
a cross reacting antibody that can’t be dissociated
What chromosome is occupied by A, B or O gene?
9
Which gene is considered amorph?
O
Phenotypes Vs. Genotypes
A or B vs. AA, BB, OO
The formation of ABH antigens results from…
the interactions of the genes at 3 separate loci
What do the ABO, Hh and Se genes code for?
to produce specific glycosyltransferases that add sugar to a basic precursor substance to make the ABH antigens
What are the type 2 precursor substances?
ABH antigens (attached to paragloboside or glycan)
Where are the type 1 precursor chains found?
body fluids, milk, plasma, urine and tears
Where is the H gene located?
chromosome 19
The amount of H antigen you have is based on…
How much sugar is added to it
What antigen will have the most H antigen?
O
If the chain only presents with fucose, what blood cell type do you have?
O
If the chain presents with fucose and GalNAc , what blood cell type do you have?
A
If the chain presents with fucose and D-galactose, what blood cell type do you have?
B
ABH soluble substances are based on ABO genes inherited and another set of genes called…
Sese (secretor genes)
The secretor gene only plays a rolf in what precursor type?
I
What is an ABO subgroup?
differs in the amount of antigen carried on red cells
What subgroup is 99.9% of all subgroups?
A
What subgroup gives you a mixed-field agglutination reaction?
A3
What is the Bombay phenotype?
individuals who don’t inherit the H gene from either parent but are blood typed as O
What are technical sources of error?
warming (inc antibody sensitization)
contamination
non-calibrated centrifuge
What are the nontechnical ABO discrepancies?
Group I (antibodies) Group II (antigens) Group III (protein) Group IV (miscellaneous)
What is chimerism?
the presence of two cell populations in a single individual
How do you perform group I discrepancy resolution?
incubate 15-30min at room temp, spin, read again and if necessary incubate at 4 degrees Celsius
Where do Rh antigens reside?
On proteins
What are some characteristics or Rh antigens?
very immunogenic
produced after exposure to foreign red blood cells
How many antigens are in the Rh blood group system?
over 50
When is Rh critical?
pretransfusion testing
Who discovered the Rh BGS?
Landsteiner and Wiener
What is the fisher-race theory?
the Rh locus contains 3 distinct genes, D, C and E
What is the Weiner Theory?
there was only one gene responsible for defining Rh that produced an agglutinogen containing a series of blood factors
What are the 5 major antigens in the fisher-race nomenclature?
D C c E e
What does Weiner use for presence/absence of D antigen?
R- present, r-absent
Describe the Rosenfield nomenclature…
D - Rh1 C - Rh2 E- Rh3 c - Rh4 e - Rh5
Describe the ISBT nomenclature…
a 6-digit number for each authenticated blood group specificity
What chromosome is Rh locus?
chromosome 1
How many Rh genes are there actually? What are they?
2, RHD, RHCE
Where is RHAG located, what is its purpose?
chromosome 6
Rh-associated glycoprotein that is a coexpressor for Rh antigen expression
The lack of RHAG is responsible for…
Rhnull
Where sre RhD and RhCE proteins and RhAG found?
exclusively on red blood cells, they help maintain structural integrity
In Rh-positive individuals, how many RhD genes do they inherit?
one or two as well as RHCE
Rh-negative individuals can arise from what three mutations?
Europeans - deletion of RHD
Africans - peudogene (RHD)
Asian - alteration in RHD that causes D-negative
what percentage of humans have the D antigen?
85%
When do you perform an indirect antiglobulin test or AHG test?
when your cells type as D-negative on immediate spin reading to ensure if Rh is not positive or “weak D”
Weak D phenotype can arise from…
genetic weak
position effect
partial D
Del
What ethnicity more commonly has genetic weak D?
African Americans
Describe C in Trans to RHD…
a position effect of weak D where the allele carrying RHD is opposite to the allele carrying C which causes the cell to look Rh negative
What’s missing in partial D?
extracellular epitopes or pieces of the D protein
Which doses can Rh show?
C and E
Which antibody subclasses show the greatest clinical significance?
IgG1 and IgG3
What prevents the mom’s Rh antibodies from attacking the fetal Rh antigens?
Rh-immune globulin
Describe the two types of Rhnulls
Regulatory- RHAG is absent or mutated (antigens not espressed)
Amorph - RHAG is normal, RHCE is mutated and RHD deleted
Describe Rhnull syndrome
individual who fail to express any Rh antigens on the RBC surface or shows severely reduced expression of all RH antigens
Describe Rhmod
individuals have partial suppression of Rh gene expression caused by mutations in RHAG gene
What is the use of saline in ABO/Rh testing?
agglutination reacting for IgM antibodies, don’t require enhancement or mods
If you have a multiple myeloma what should you use for testing?
low protein anti-D, autoantibodies
Describe the use of LISS in ABO/Rh testing…
to lower the zeta potential so that they can agglutinate better
Which antibodies don’t require LISS?
IgM
Describe the use of albumin in ABO/Rh testing…
aka potentiators that inc the dielectric constant which reduces the zeta potential
has a colloid solution (albumin, PEG (don’t spin), Polybrene, PVP, Protamine)
What are the two classes of AHG reagent?
Monospecific
Polyspecific
Describe AHG monospecific reagent…
one antibody (anti-IgG or anticomplement (anti-C3b, anti-C4b, anti-C4d)
In polyspecific AHG reagent, which antibodies does it have?
anti-IgG, anti-C3b, anti-C4b and anti-C4d
How are monoclonal AHG reagents produced?
hybridoma technology
How is polyclonal antisera produced?
injecting animals with human globulin components and then collecting antihuman antibodies
What is the focus of antibody detection method?
first test on antibodies to detect unexpected or irregular antibodies
What are expected antibodies?
naturally occurring antibodies without exposure to RBCs
What are unexpected antibodies?
produced in stimulation to red blood cell (transfusion, pregnancy or transplantation)
What are immune antibodies?
result of exposure to RBC antigens
What are naturally occurring antibodies?
result of exposure to environmental sources, ex. pollen, fungus and bacteria
What are passive (acquired) antibodies?
antibodies produced in one individual and then transmitted to another via plasma-containing blood
What are autoantibodies?
antibodies directed against the individuals own RBCs, react with high-incidence RBC antigens
What are alloantibodies?
produced after exposure to genetically different or non-self, antigens
What are warm antibodies?
typically IgG
react best by indirect antiglobulin technique
don’t directly agglutinate saline-suspended RBCs after 37 degrees Celsius
When do cold antibodies work best? What antibodies are they?
4 degrees Celsius (IgM)
IAT is trying to answer the question of…
Does that patient have an antibody, if so is it clinically significant
What are the phases of testing?
Immediate spin
incubation phase
AHG phase
Screen cells are reagent red cells from blood group…
O
