BB - Day 2 Flashcards
Define “naturally occurring” antibodies. What two types of antibodies are considered naturally occurring?
Targets antigens on RBCs due to similarity to a naturally occurring target in nature
-unknown mechanism, possibly gut bacteria
anti-A and anti-B
ABO - which phenotype is the rarest?
AB
Naturally occurring antibodies - can they cross the placenta? Why or why not?
No - predominantly IgM
-except anti-A,B, which is IgG
ABO - which phenotype is the universal RBC donor? Universal plasma donor? Universal recipient?
RBC donor = O negative
-can only take other O blood
Plasma donor = AB
-no antibodies against A or B antigens
Recipient = AB
Can newborns be forward typed and back typed?
Forward = yes
Back = no, only maternal antibodies present at birth
-wait >6 months
At what temperature do ABO antibodies react best?
Room temperature or colder
The immune form of ABO antibodies are produced during (2)…
Transfusions
Pregnancy
-these events expose patients to foreign blood cells
Anti-A,B antibody is produced only by this ABO phenotype
O
Which ABO antibody(ies) can frequently cross the placenta? Why?
Mostly anti-A,B since they are predominantly IgG
A and B antigens are composed of… Their precursor is…
Carbohydrates
H antigen
Which gene codes for H antigen?
H gene
- independent of ABO genes
- H is dominant; one copy can make H antigen (Hh)
A person that’s hh phenotype can’t make what antigens… Another name for the hh phenotype
H antigen, A antigen, and B antigen
-H antigen is a precursor to A and B; cannot make H = cannot make A or B
Bombay
A person’s H precursor levels are highest in this ABO phenotype. Why?
O
No A or B antigens on O cells, so a lot of residual H
A Bombay patient should receive a blood transfusion from another person with this blood type… Why?
Bombay
Bombay patients make anti-H against all other ABO groups
- anti-H is naturally occurring
- forward = A and B negative
- reverse = anti-A1, anti-B, anti-O positive
Besides RBCs, ABO antigens are also found on… What is this significance?
Endothelium, kidney, heart, bowel, pancreas, lungs
Can cause extravascular hemolysis
A person is considered a secretor when they can secrete these antigens in all bodily secretions… The secretor system involves which two blood group systems?
A, B, H
ABO and Lewis
What percent of the US population are secretors?
80%
To be a secretor, a person must have one of these genotypes… People that are non-secretors have this genotype…
SeSe or Sese (dominant phenotype)
sese
A1 vs A2 - which is more common?
A1 = “normal” A
A1 reacts with which anti-A antibodies? A2 reacts with which anti-A antibodies?
A1 = anti-A, anti-A1
-A1 cells have A and A1 antigens
A2 = anti-A only
-A2 cells have A antigens only
Dolichos biflorus will agglutinate this cell
A1 cells
anti-A1 lectin
A1 and A2 can be distinguished via forward or reverse typing?
Reverse typing only
Ulex europaeus will agglutinate A1 or A2 cells? Why?
A2 cells
-U. europaeus = anti-H lectin
A2 has more precursor H than A1
-incomplete conversion to A antigen = more remaining precursor H
anti-H antibody - what class of antibodies?
IgM - reacts best under room temp, can bind complement
-similar to other ABO antibodies
What blood should be given to A2 patients?
A2 or O
-A2 patients make anti-B and anti-A1 antibodies, but not anti-A antibodies
anti-H antibody reacts strongest and weakest with these ABO phenotypes
Strongest = O (high precursor H)
Weakest = A1B (low precursor H)
-suspect anti-H antibody if O cells are reactive but A cells are not
General rule in the lab - should we drop cells first or solution first?
Drop solution first, cells second
- so you know you’ve already added it
- so you don’t contaminate reagents
Why are A1 cells normally used for reverse typing?
A1 cells contain high number of A antigens
If there’s a discrepancy and the reverse typing does not match the forward typing what can we do with our test tubes?
Let samples sit for 15 mins at room temperature, then re-spin tubes
-weak positive for reverse typing not good enough
Depressed antibody production affects forward or reverse typing?
Reverse
- seen in newborns, elderly, leukemias
- lower or nonexistent antibody production
What is the “acquired B” phenomena? How is it treated?
Bacterial enzymes convert A antigen to B antigen, so patient’s anti-B antibodies attack cells
Acidify patient’s sera
Where can one find Wharton’s jelly?
On baby’s cord blood only
- mucopolysaccharide that sticks to RBCs
- need multiple washing to get rid of
A2 patients show a reverse typing that looks like… Why?
O
A2 patient has anti-B and some anti-A1 antibodies naturally because A2 cells have A antigens but no A1 antigens
-A1 patients have both A antigen and A1 antigen
What is the name of the A antigen sugar? What is the name of the B antigen sugar?
N-acetylgalactosamine
D-galactose
HDFN is caused primarily by the antigen group
Rh
Rh - what are the 5 major antigens?
D, C, c, E, e
What does little ‘d’ signify in the Rh group?
Lack of D antigen
-little ‘d’ is NOT an antigen
Are homozygous or heterozygous antigens stronger?
Homozygous = more binding sites
What should we do if our anti-D and Rh control tubes are both negative?
Do a weak D test
-15 min at 37C, 3x wash, AHG
Weak D is caused by (3)…
Genetics - person makes fewer D antigen
C Trans - allele carrying D trans to allele carry C
-Dce/dCe
Partial D (mosaic D) - missing piece of the antigen
Rh antibodies are what class of immunoglobulins? When are they produced?
IgG
After exposure due to transfusion or pregnancy
-not naturally occurring
What temperature do Rh antibodies react optimally?
37C
- anti-D = IgG, reacts best at 37C
- that’s why we heat 37C for 15 min in weak D test
Do Rh antibodies cause intravascular or extravascular hemolysis? Why?
Extravascular only
Rh CANNOT bind complement
Can Rh antibodies cross the placenta? Why?
Yes
They are IgG
Rh-negative mothers are automatically given ___ at the 28th week of pregnancy to prevent ___
RhIg (RhoGAM) - an anti-D antibody
Sensitization to Rh-positive baby, making anti-D antibodies
- can make IgGs that cross placenta and attack baby’s cells, causing extravascular hemolysis (HDFN)
- given even if we don’t know baby’s Rh status yet
Is Cw expressed on big C or little c?
Both
- allele on C/c locus
- low frequency antigen
Which 2 Weiner phenotypes are the rarest?
Rz and r^y
