RH BLOOD GROUP SYSTEM Flashcards
(33 cards)
Antigens of the Rh system
_____- refer only to presence or absence of the Rh antigen D on the red blood cell
●“Rh pos” and “Rh neg” are old terms, although blood products still labeled as such
●Early name “Rho” less frequently used
● Four additional antigens:______
●Named by Fisher for next letters of alphabet according to precedent set by naming A and B blood groups
●Major alleles are C/c and E/e
“D positive” and “D negative”
C, c, E, e
________-, after A and B, is the most important RBC antigen in transfusion practice
●Individuals who lack D antigen DO NOT have ____
- produced through exposure to D antigen through transfusion or pregnancy
●Immunogenicity of D greater than that of all other RBC antigens studied
● Has been reported that >80% of D neg individuals who receive single unit of D pos blood can be expected to develop immune anti-D
____- is routinely performed so D neg will be transfused with D neg
D antigen
anti-D
Testing for D
Rh system IDENTIFIED by ____(2) in ___(year)
●Immunized animals to Rhesus macaque monkey RBCs
●Antibody agglutinated 100% of Rhesus and 85% of human RBCs
●Reactivity paralleled reactivity of sera in women who delivered infant suffering from hemolytic disease
●Later antigen detected by rhesus antibody and human antibody established to be dissimilar but system already named
Landsteiner and Wiener
1940
• Suggested that antigens are determined by 3 pairs of genes which occupy closely linked loci
• Each gene complex carries (3)
• Each gene (except d, which is an amorph) causes production of an ___
Fisher - race
D or its absence (d), C or c, E or e
antigen
MANY variations and combinations of the 5 principle genes and their products, antigens, have been recognized
_____- account for majority of unexpected antibodies encountered
_____- stimulated as a result of transfusion or pregnancy, they are immune
Rh antigens and corresponding antibodies
Rh antibodies
Key observation of ____(2) in ____(year) that the delivery of stillborn fetus and adverse reaction in mothers to blood transfusion from father were related
●Syndrome in fetus is now referred to as _______
- Syndrome had complicated pregnancies for decades causing severe jaundice and fetal death.
●Erythroblastosis fetalis (HDN) linked with Anti-Rh by Levine in 1941
Levine and Stetson
1939
Hemolytic disease of the fetus and newborn (HDFN)
“Erythroblastosis fetalis”
• Three loci carry the Rh genes are so closely linked that they never separate but are passed from generation to generation as a unit or gene complex
Below an offspring of the
Dce/dce individual will inherit EITHER _____ from the parent,
never dCe as this would indicate crossing over which does not occur in Rh system in man.
Dce or dce
With the exception of __ each allelic gene controls presence of respective antigen on RBC.
____- would cause production of the D, C and e antigens on the red cells.
● If the same gene complex were on both paired chromsomes (DCe/DCe) then only ______ would be present on the cells.
● If one chromsome carried DCe and the other was DcE this would cause _____ antigens to be present on red blood cells.
● Each antigen except __ is recognizable by testing red cells with specific antiserum.
d
The gene complex DCe
D, C and e
D, C, c, E and e
d
- Postulated that TWO genes, one on each chromosome pair, controls the entire express of Rh system.
● Each gene produces a structure on the red cell called an ______
● Eight (8) major alleles (agglutinogens): _____
● Each agglutinogen has 3 factors (antigens or epitopes)
●The three factors are the antigens expressed on the cell.
●For example the agglutinogen R0= Rh0 (D), hr’ (c), hr’ (e)
● Each agglutinogen can be identified by its parts or factors that react with specific antibodies (antiserums).
Wiener
agglutinogen (antigen).
R0, R1, R2, Rz, r, r’, r” and ry
The two theories are the basis for the two notations currently used for the Rh system.
● Immunohematologists use combinations of both systems when recording most probable genotypes.
● You MUST be able to convert a Fisher-Race notation into Wiener shorthand, i.e., Dce (Fisher-Race) is written ___
● Given an individual’s phenotype you MUST determine all probable genotypes and write them in both Fisher-Race and Wiener notations.
__ is the most common D positive genotype.
___ is the most common D negative genotype.
R0
R1r
rr
In ___ proposed a nomenclature based ONLY on serologic (agglutination) reactions.
● Antigens are numbered in the order of their discovery and recognition as belonging to the Rh system.
● No genetic assumptions made
● The ___ of a given cell is expressed by the base symbol of “Rh” followed by a colon and a list of the numbers of the specific antisera used.
● If listed alone, the Antigen is present (Rh:1 = ___)
● If listed with a __, antigen is not present (Rh:1, -2, 3 = DcE)
● If not listed, the antigen status was not determined
● Adapts well to computer entry
1962
phenotype
D Ag
“-”
__ is the most important blood group system after ABO in transfusion medicine
• One of the most complex of all RBC blood group systems with more than 50 different Rh antigens
The genetics, nomenclature and antigenic interactions are unsettled
Rh
____- International organization created to standardize blood group system nomenclature.
• Assigned 6 digit number for each antigen..
◦ First 3 numbers indicate the blood group system,
eg., 004 =
◦ Last 3 numbers indicates the specific antigen,
eg., 004001 =
• For recording of phenotypes, the system adopts the Rosenfield approach
ISBT international society of blood transfusion
Rh
D antigen
_____ is the result of the reaction between the red cells and antisera
_____ is the genetic makeup and can be predicted using the phenotype and by considering the race of an individual
• Only family studies can determine the true genotype
phenotype
genotype
Phenotyping and genotyping
Five reagent antisera available.
◦ Only ___ required for routine testing.
◦ Other typing sera used for typing rbcs to resolve antibody problems or conduct family studies.
• Agglutination reactions (positive and negative) will represent the ____
• No anti-d since d is an ____.
• Use _______ to determine most probable genotype.
anti-D
phenotype
amorph
statistical probabibility
Rh phenotyping
Uses (4)
◦
• Protocol
◦ Mix unknown RBCs with Rh antisera
◦ Agglutination indicates presence of antigen on cell and determines phenotype.
◦ Use published frequencies and subject information to determine genotype.
Parentage testing
◦ Predicting hemolytic disease of the fetus and newborn (HDFN)
◦ Confirmation of Rh antibody specificity
Locating compatible blood for recipients with Rh antibodies.
Phenotyping and genotyping
Molecular testing becoming more popular:
◦ Cannot use ___ on recently transfused individuals, molecular testing can differentiate.
◦ Anti-sera not available for some antigens, molecular testing being developed for all blood group genes.
◦ D zygosity can be determined.
◦ Fetal genotyping for D can be done on ____
◦ Monoclonal reagents from different manufacturers react differently with variant D antigens, molecular test specific.
____ continue to be the “gold standard” but this will change in the future.
anti-sera
fetal DNA present in maternal plasma.
Typing sera
____ - Refer to textbook.
____ are listed as “presumptive” or “most probable”.
• Genotypes will vary in frequency in different racial groups.
Genotype frequencies
Genotypes
Not all D positive cells react equally well with anti-D.
• RBCs not immediately agglutinated by anti-D must be tested for ____.
◦ Incubate cells with anti-D at ___, coating of D antigens will occur if present.
◦ Wash X3 add AHG
◦ AHG will bind to ___ coating cells if present.
◦ If negative, individual is D negative
◦ If positive, individual is D positive
weak D
37C
anti-D
3 mechanism of Weak D?
• Results in differences from normal D expression ◦
____- (inherited weak D or position effects)
____- (mosaic D; could produce Anti-D)
Genetic
• Position effect
• Mosaic
Quantitative
Qualitative
Two systems of nomenclature developed prior to advances in molecular genetics
• Reflect serologic observations and inheritance theories based on family studies
• Because these are used interchangeably it is necessary to understand the theories well enough to translate from one to the other
• Two additional systems developed so universal language available for use with computers
The order of loci on the gene appears to be ___ but many authors prefer to use “CDE” to follow alphabet
• Inherited from parents in linked fashion as _,,
• The gene __ is assumed to be present when D is absent
“DCE”
haplotypes
d
• C trans - position effect; • The D gene is in trans to the C gene, eg., C and D are on OPPOSITE sides: Dce/dCe • C and D antigen arrangement causes steric hindrance which results in weakening or suppression of D expression.
