Lecture 5: Rh System-D Flashcards
Outside of the ABO system, the D antigen is the most __________ antigen… because Rh alloimmunization is IgG mediated, transfusion reactions are primarily extravascular. The patient may have a fever, jaundice, icteric sclera, dark urine or a drop in hemoglobin.
immunogenic
What is the Rh interpretation of this:
Anti-A: 0
Anti-B: 0
Anti-A, B/ Anti-D: 0, 4+
A1 cell: 4+
B cell: 4+
O pos
In 1937: Guinea pigs and rabbits injected with Rhesus monkey RBCs because these were common animals for experimentation. In 1940: Once the antibody was isolated from the rabbits, the antibody was agglutinated with human cells.
Antibody formed that reacted with 85% of human RBCs. The antigen called the Rhesus or ____ factor
Rh
In 1963, Rabbit source anti-Rh reactivity did _____ match human source anti-Rh.
Rabbit source anti-Rh was positive on all newborn cells even those found to be negative for human anti-Rh. Rabbit source anti-Rh was renamed LW in honor of Landsteiner and Weiner (who did not like that it was named this.)
NOT
The Characteristics of LW system: LW antigens are more abundant on Rh _______ than Rh negative red cells.
positive
-Antigens can be depressed in Lymphoma, pregnancy
The Characteristics of LW system: Gene is on Chromosome ___ and belongs to ICAM family responsible for erythrocyte adhesion to macrophages for expulsion of their nucleus during maturation.
19
-Two alleles: LWa (high incidence) LWb (low incidence
-LWb more common in Finns
Utilize the history of this antigen system to differentiate between Rh blood system, RHAG and LW blood system.
RH System:
Anti-D human
-Highly immunogenic
-causes HDFN and TRXN
Intrinsic protein to human RBC
-Resistent to DTT and Enzymes
D antigen is present or absent from cell with little structural change.
Name the antithetical antigen pairs in the Rh system and their relative population frequencies in Caucasian, Black and Asian populations of the United States.
- Most polymorphic system of the human antigens
-second most clinically significant antigen
–>Transfusion reactions are hemolytic
–> HDFN #1 cause
-Most “immunogenic” antigen - exposure causes antibody formation estimated 80% of the time in healthy individuals
- Variable frequency based on race:
–> Caucasian= 80%
–> Black = 95%
–> Asian = ~100%
Autosomal Dominant inheritance
No alleles: Antigen is either present or not
–> Many mutants of D have been found, especially in the Black community.
Before 1960s lots of baby deaths due to maternal incompatibility with infant (HDFN). Rhogam is a commercial made low dose anti-D shot. Prevents real (allo) anti-D from _____ in mothers.
forming
What is the red cell shape of Rhnull
Stomatocytes
Antigen is an _______ protein to the RBC membrane.
-Non Glycosylated
-Small variable portions on outside of the membrane
-ONLY on RBCs (not on other cells)
intrinsic
-Begin developing on RBCs as early as 16 weeks from conception, well developed at birth.
-Role: Membrane structure
–> Transport ammonia or CO2 (cations)
Rh postive - D antigen is _______
expressed
Rh postive - D antigen is _______
not expressed
“Weak D” Du - Antigen expression is _____ that it requires _________ (AHG phase testing ) for detection
low, enhancement
“Partial D” - Antigen expression is _____ depending on the reagent.
variable
Rh postive - D antigen is expressed in 10000-200000 antigens on the red cell. Antigen is so pleomorphic that FDA requires serological reagents to be _________. Autosomal Dominant inheritance of at least 1 RHD gene from a parent.
Reagent anti-sera reacts at ___________ with patient cells
polyspecific, room temperature
Rh negative - D antigen not expressed on Red cell at all. Autosomal recessive inheritance of a non functioning RHD gene from _____ parents. The gene differs based on ancestry.
both
European ancestry - ________ of RHD gene
deletion
You don’t have it
African ancestry - RHD gene with _____ mutations that does not produce the D protein.
missense
(cause a mutation)
Asian ancestry - “Del) mutant RHD gene that results in expression of the antigen that is so ____ serologically that it can only be detected through __________/elution. 10-30%
low, adsorption
( you have to do extensive testing to even find it)
“Weak D” Du- Previously thought to be a new allele but no anti-Du is ever made.
Complete D expression but in _____ quantity.
Mutations occur in transmembrane portion of protein, not the part on outside.
DO NOT make anti-D
lower
Reagent antisera reacts <2+ with patient cells at room temperature
DO NOT make anti-D
“Partial D” is far less _______ than Weak D in Caucasians more in ________.
common, blacks
Parts of D are missing on outside of cell due to mutations in RHD gene
CAN make anti-D to the missing portion - Reagent antisera might react positive or negative with patient red cells.
Using the antigens structure on the cell, explain the serological and immunological difference between a patient who is “weak D” and “partial D”
Who can make anti-D?
a) Del
b) Du
c) D negative
d) D partial
C and D
All or part of the antigen is missing from the patient cell. If the patient sees the normal antigen they will view it as foreign. Potentially stimulating antibody production.
Immune stimulated = from ______ or _______
transfusion or pregnancy
Clinically significant = associated with HTR and HDRN.
What is HTR and HDRN?
HTR: hemolytic transfusion reaction
HDRN:hemolytic disease of fetus or newborn
Immunogenic = exposure to antigen positive cells results in antibody development in 80% _____ individuals. ( 21% in hospitalized individuals)
healthy
Dosage affect = weaker reactivity on cells that only have ____ dose of the antigen
1
Example: D/d
Define the properties of the red cell antibodies in the system regarding Ig call, reaction, temperature, clinical significance for transfusion reaction and HDN, and immune stimulation and compliment binding ability.
Characteritics
-Most are IgG1
-May be detected at 37C but most frequently detected by IAT
-Enhanced by testing with
–> enzyme treated cells
–> LISS
–>PEG
–>High protein
-DTT does not minimize activity
-Do not bind complement
-Crosses the placenta
Do Rh negative babies make anti-D?
No. They have not been stimulated to make the antibody and their immune system has not been fully developed.
RHAG: Rhesus Associated Glycoprotein.
-Other name: RH50, RH2, Rhesus associated polypeptide.
-Rh antigens exist as a multi-subunit complex of CD47, LW and glycophorin B
-Gene is on Chromosome ___. Ancestral protein to RHD and RHCE.
6.
Function:
1) Regulated Cation Transport of Ammonia
2) Stabilize Rh antigen expression on cell through protein-protein interaction
Link lipid layer to ankyrin skeleton core.
Basically RHAG helps the anti-D to get on the cell.
RhD gene is found on Chromosome ___
1
Also here facing opposite is RHCE gene
-Rhesus boxes flank the D gene which are the deletion point for Rh negative expression in Caucasians.
-D expression is _______, if one gene is inherited, it will be expressed.
-No alleles for D. Absence of D gene is indicated in the literature by “d”
-9 coding epitopes expressed on outside of cell.
dominant
Heterogeneity of D antigen occurs because of nearness to the _____ gene
CE
-Similar codes (differ by 32-35 amino acids)
-Coding is opposite for the two genes 3’ -> 5 & 5’->3’
-Fold over during replication allows for much crossover
Which antibody reacts with Rhesus - baby cells but not Rhesus adult cells?
A) Anti-D
B) Anti-C
C) Anti-Du
D) Anti-LW
D) Anti-LW
A patient has developed multiple antibodies to the Rh system. Anti-D, Anti-C, and Anti-E. How many units do I have to test to find compatible blood?
A) 33 units
B) 15 units
C) 3 units
D) 1 Rh negative unit
D) 1 Rh negative unit
An individual has the following Rh phenotype: D+ C- E+ c+ e- Using Fischer/Race terminology what is the most genotype if they are Asian?
A) DcE/DcE
B) DCe/DCe
C) DCe/dce
D) DcE/dce
A) DcE/DcE
How are weaker than average reactions with anti-D categorized for donor’s cells?
A) Rh positive
B) Rh negative
C) Rh null
D) Weak D
A) Rh positive
Which population is the weak D test performed in?
A) Baby
B) Elderly
C) Cardiac
D) Prenatal
A) Baby
We are concern if they have the possibility of becoming donors.
What antibodies do you expect to find in a patient’s plasma who has never been pregnant or transfused and has the following serological results?
Anti-D: 4+
Anti-C: 4+
Anti-c: 0
Anti-E: 4+
Anti-e: 0
A) None
B) Anti-D, Anti-C, Anti-E
C) Anti-c, Anti-e
D) Anti-D only
A) None
Which patient would you expect to make anti-D?
A) Patient who is pregnant and molecular tests as D mosaic
B) Patient who weakly reactive D results in serological testing
C) Patient who has already made anti-c
D) Patient who is immune compromised and transfused Rh positive blood.
A) Patient who is pregnant and molecular tests as D mosaic
How is testing for Rh antigens and antibodies different from ABO testing?
A) ABO antigens only require room temperature incubation for detection whereas Rh antigens require AHG for detection
B) Rh antibodies are naturally occurring and are usually present in patient plasma whereas ABO antibodies are not
C) ABO antibodies can be tested at room temperature whereas D antibodies require AHG for detection
D) It is not different. They are the same.
C) ABO antibodies can be tested at room temperature whereas D antibodies require AHG for detection
Which genotype shows the strongest reaction with anti-D?
A) DcE/DcE
B) DCe/DCe
C) D–/D–
D) Dce/Dce
C) D–/D–
Super D exzolted
Rh null cells are which of the following ?
A) Shaped like Stomatocytes
B) Serotype as D-C-c-E-e+
C) RhAG postive
D) Highly immunogenic
A) Shaped like Stomatocytes
