nada mohamed ahmed, md, mt (ascp)i 16-2-2015. objectives
TRANSCRIPT
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Nada Mohamed Ahmed ,MD, MT (ASCP)i
16-2-2015
Rh BLOOD GROUP SYSTEM
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OBJECTIVES
• History
• Classification/Nomenclature System• Genetices• Nomenclature systems• Rh Antigens
• Rhesus Antibodies
• Clinical Significance of Rh Antibodies.
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Rh BLOOD GROUP SYSTEM
• discovered in 1940 by Landsteiner & Wiener
• most complex erythrocyte antigen system; located on chromosome 1
• found exclusively on surface of RBC integral part of red cell membrane
• primary antigen if present, consider Rh (+)
• lack corresponding naturally-occurring antibodies in serum
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Rh BLOOD GROUP …
• Complex blood group with >50 described antigens
• Rhesus monkey• D Ag is more potent• No natural Ab against Rh• Nomenclature systems
– Fisher-Race (English)– Wiener (American)
Deepa Babin @TMC Kollam
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Rh BLOOD GROUP SYSTEM
Rh Antigens• with two integral membrane proteins
1. RhD
2. RhCcEe
• D antigen resides in RhD protein most immunogenic followed by c, E, C and e
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Rh BLOOD GROUP SYSTEM
Weak D Antigen (Du)
• Rho variant
• weak or absent red cell agglutination by anti-D detected only with use of anti-human globulin reagent use bovine anti-D
• weakened form caused by 1 of 3 situations:
1. a piece of the D antigen is missing
2. D gene is on a chromosome opposite a C gene (+) steric hindrance
3. Inheritance of a gene coding for less D antigen
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Rh BLOOD GROUP SYSTEM
• Presence of D = presence of Rho factor Rh (+)
• Absence of D Rh (-)
A person is grouped as Rhesus (Rh) positive or negative based on the presence or absence of antigen DRh positive: a person who inherits gene D and the red cell express antigen D.Rh negative: a person who does not inherit gene D and the red cells do not express antigen D
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The antigens of the Rh-Hr blood group system
• The Rh antigens can be demonstrated on fetal red cells as early as 38 days after conception, and are well developed at birth.
• There are five rhesus antigens, D, C, c, E &e which are only expressed on red cells.
• The ‘d’ gene is not expressed and there is no ’d’ antigen, it only implies the absence of ’D’.
• They are not found in body fluids (like saliva, amniotic fluid) and not detected on leucocytes or platelets.
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Individuals who lack any of these antigens may be stimulated to produce the corresponding antibodies (anti-D, anti- C, ant -c, anti-E, anti-e) by transfusion or pregnancy.
Antigen D, having antigen site between 110,000 and 202,000 per erythrocyte.
Cont.....
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Variants of antigen
Weak antigen D (Du)• Weak forms of antigen D where the
number of D sites on the red cells is reduced.
• There are two grades of Du:• High grade Du red cells, which are
agglutinated by certain anti-D sera.• lower grade Du red cells, which are
agglutinated only by the Indirect Antiglobulin (IAG )test.
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Rhesus Antibodies
• Result from the exposure to Rh antigens• IgG form which most of them are IgG1 or IgG3
subclasses.• Bind at 37°C• The common Rh antibodies are anti –E, anti -e,
anti -C,anti-c and anti –D.
• Rh antibodies generally develop from 2 to 6 months after the initial immunization by red cells.
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• Cause severe hemolytic transfusion reaction in a recipient if transfused with blood possessing the
Rh antigen. • Rh antibodies being IgG, are capable of crossing
the placenta and are associated with HDN.
Clinical Significance of Rh Antibodies.
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Rh BLOOD GROUP SYSTEM
CLASSIFICATION/NOMENCLATURE SYSTEM
Fischer & Race
• Three alleles: D/d, C/c and E/e
• Five antigens: D, C, E, c, e
• d no D locus no antigenic products
Rosenfeld
• Numerical system
• Rh1 to Rh5
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Rh Groups: Fisher-Race
Anti-e
Anti-C
Anti-D
genes
linked
closely-
e
C
D
AbAgChromosome
e
C
D
5 major antigens: D, C, E, c and e 14
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Rh Groups: Weiner
Rh1
hr”
Anti- hr’hr’
Anti-rh”rh”
Anti-rh’rh’
Anti-RhoRho
AbAgCHROMOSOME
R1 single gene
Anti- hr”
5 major antigens: Rho, rh’, rh”, hr’, hr”
15
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Converting Wiener into Fisher-Race or Vice Versa
R Dr no D
1 and ‘ C
2 and “ E
Example: DcE R2
r” dcE
Written in shorthand
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Rh BLOOD GROUP SYSTEM
Testing for Rho (D) Antigen:
• use antisera originating from human source
• Antisera with different constituents use of high protein media necessary to produce agglutination since antigens are an integral part of the red cell membrane less numerous than ABO antigens
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The Rh- Hr Blood Grouping Technique
• Slide Test Method
• Modified Tube Test Method
• Du Typing Using Indirect Anti- Globulin Test
(IAT)
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