Rh and LW Blood Groups Flashcards
Rh Positive
Presence of D antigen
Example: Group A+ means A blood type with Rh antigen
85% of population
Rh Negative
Absence of D Antigen
Example: Group O- means O blood type with no Rh antigen
15% of population
Discovery of D Antigen
1939-1943
Anti D
Described in HDN (Hemolytic Disease of the Newborn)
Anti-Rhesus
LW
Not the same as Anti D
Rh Gene
Chromosome 1
Autosomal Dominant
D antigen present
RBC only
D Clinical Significance
Second in significance
High Immunogenicity
Other Rh Antigens
Approx 50
5 most often seen - D, C, c, E, e
Wiener Nomenclature
Genes indicated by single letter
Gene product: agglutinogen
Gene product + subscript: haplotype
Factors: Individual antigens
Fisher Race Nomenclature
1 gene and 1 product per allele
Letter designations
Most often used
Tippet Theory
Two closely linked loci
Used in research
Fisher-Race Theory
Three closely linked loci inherited as a unit
Most common system
Wiener Theory
Single locus with multiple alleles
Most difficult
Rosenfield/Tippit
Antigens numbered in order of discovery/assignment to Rh system
Dosage Definition
Amount of antigen present on homozygous cell vs amount of antigen present on heterozygous cell (weak AHG rxn)
Genotype determination
Can estimate genotype based on reaction strength of phenotyping results
R2 cells
cDE - one haplotype
Stronger expression of D
React more strongly with anti-D reagent
Only scenario with enhanced antigen reactions
Cis Effect
Labilization of ligands that are cis to other ligands
Cis Meaning
On the same side
Example: cDE - D and E are cist to each other
- E antigen produced by R2 gene (cDE) is weaker than E antigen produced by r” gene (cdE)
Trans Effect
Comparison of antigens on both sides of the genotype
Trans Meaning
On opposite sides
Example: C and E antigens are weaker in:
- R1(CDe)/R2(cDE) individuals C is trans with E but cis with D
- R1(Cde)/r(cde) - C is not cis or trans with either d, c, or e
- R2(cDE)/r(cde) - D is cis with E but no trans
Possible Causes of Weak D expression
Due to Transmissible Gene Inheritance
- Less antigen sites
Positive Effect
- C gene in trans to D (weaker D antigen expression)
Partial D, D Mosaic, D Variant
- Lack a part of D antigen
Weak D Notation
Du
Weak D Clinical Significance for Donors
Weak D less immunogenic
- Weak D cells destroyed by anti D
Weak D Clinical Significance in Recipients
Not necessary to test for weak D
- Receivin Rh neg blood doesn’t affect a person
Cis Product Antigens
Ce (rhi) - R1 gene (CDe)
Ce on same haplotye
CDE/cde does not produce Ce (rhi)
c and e on same haplotye
cDE/CDe does not have f antigen
G Antigen
Present on most D pos and all C pos cells
Appears to be anti C and anti D (cannot be separated)
Rh neg person can make anti-G to the G antigen
Gene Deletions
Rare
Lack of activity at Cc and/or Ee sites
Cels may show very strong D activity
LW Antigens
Present on most human RBCs
D neg cells have waker LW activity
Anti LW
Reacts with D pos cells
Weakly with D neg cells
Rh Null
Very Rare
No Rh antigens
Absence of Regulator Gene
RBC membrane abnormalitys
MUST transfuse with Rh Null Blood
Rh Antibodies
Anti-D
Anti-C
Anti-c
Anti-E
Anti-e
Rh Antibodies Result
Immunization (exposure)
Immunogenicity e<C<E<c<D
False Positives in Rh Testing
Wrong reagent added
Contaminating Antibody
Polyagglutinable RBCs
Autoagglutinins/Abnormal Proteins (Multiple Myeloma)
Contaminated Reagent
False Negatives in Rh Testing
Wrong Reagent Added
Reagent Not Added
Variant Antigen
Procedural
Weak Agglutination
Contaminated Reagent
When is it necessary to use an Rh (D) control?
Using High protein anti-D reagent (albumin)
What situations would cause a false positive reaction when doing Du testing?
Individual who has a positive DAT
Rh negative mother who has experienced a large fetal-maternal hemorrhage from Rh positive child
What is the best way to elminate cell agglutination due to Wharton’s Jelly?
Wash cells multiple times (4-5)
What are the possible causes of the following reactions:
patient cells + anti-D: 3+
patient cells + Rh control: 2+
Positive DAT
Rouleaux
What are the possible causes of the following reactions:
patient cells + anti-D: 0
above tube + anti IgG AHG: 0
above tube + Coombs Check Cells: 0
Rh type cannot be determined
Inadequate washing of cells may have occurred
Inactive AHG reagent
Rh testing and obtain the following results:
patient cells + anti-D: 3+
patient cells + Rh control: 3+
What is the next course of action?
Repeat the Rh typing with saline D or a chemically modified D antisera
An 18 yr old female is admitted to ER following a serious accident. She has had no pregnancies, no history of transfusion, and is on no mediation. Her ABO/Rh testing:
patient cells + anti-A: 3+
patient cells + anti-B: 0
patient cells + anti-A,B: 3+
patient cells + anti D: 0 this tube + anti IgG AHG: 2+
patient cells + Rh Control: 0 this tube + anti IgG AHG: 0
Tube + CC: 2+
patient serum + A1 cells: 0
patient serum + B cells: 3 +
Patient is weak D positive, report as Rh pos
Red cells type as weak D (Du) positive. The phenotype results follow. What is the most likely genotype?
Anti-C: 2+
Anti-c: 2+
Anti-E: 0
Anti-e: 2+
DCe/dce
A patient is found to be Group O, Rh positive. They also have an anti-c in their serum. What is the most probable genotype of this patient? What type of blood must be transfused to this patient?
DCe/DCe; must be transfused with blood that is c negative
