Rh blood group system overview
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BY Ms. Monica Viernes RMT
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Rh blood group system overview
- 16. # of D antigen sites Rh phenotype 990,0-146,00 R 1 r 120,00-200,00 R 0 r 140,00-166,00 R 2 r 145,00-193,00 R 1 R 1 230,00-310,00 R 1 R 2 158,00-333,00 R2R2 110,000-202,000 D--
Editor's Notes
- Most extensive blood group..with more than 50 different antigenic specificities.. With ABO discovery there were still a lot of casualties in transfusion medicine.. Subsequently an antibody was isolated from the mother’s serum that react both at 37°C and 20 °C with the father’s red cells. It was postulated that the fetus and the father possessed a common factor that the mother lacked . While the mother carry the fetus, the mother was exposed to this factor and subsequently built up an antibody that reacted against the transfused red cells from the father and resulted in hemolytic transfusion reaction
- Rhesus monkey RBCS reacts with humans..they named it rh. . Landsteiner and Wiener reported on an antibody by guinea pigs and rabbits when they were transfused with rhesus monkey red cells.
- Co-dominant..DCE because C is in between d and e locus.
- Five letter designations.. C/c and E/e are antithetical (e.g., can‟t have both C and c or E and e from same chromosome) 2) Eight potential combinations based on presence of genes for above antigens (ie, “DCe”, “dce”, etc.)
- Wiener believed that, the gene responsible for defining Rh actually produced an agglutinogen (a substance that stimulates the production of an agglutinin , thereby acting as an antigen ) that contained a series of blood factors. The agglutinogen may be considered the phenotypic expression of the haplotype. Each factor is an antigen recognized by an antibody . Antibody can recognize a single or multiple factors ( Ag )
- Believed that main Rh genes (for presence or absence of D, for C or c and for E or e) inherited as one genetically linked group, or “haplotype.” 3) Shorthand names to the haplotypes; nomenclature is still in use and is essential to know (though theory of how these are inherited has been disproven).
- Only four of the above combinations occur with significant frequency: R1, R2, R0 and r. (~97% of blacks and whites use only these four). • R0 most common in blacks, least common in whites. • r is always second in frequency. • R1 always comes before R2. Whites: R1 > r > R2 > R0 Blacks: R0 > r > R1 > R2 R1 > R2 > r and R0. Asians
- In 1960s Rosenfield proposed a system that assigns a number to each antigen of Rh system in order of its discovery or recognized relationship to the Rh system. This system has no genetic basis but simply demonstrates the presence or absence of the Ags on the red cells.
- You have until 53 in your book..
- Ag production..two theories: wiener single gene single antigen with many factors Ficher race 3 different genes Integral part of RBC membrane (Rh null people have mild hemolytic anemia) Commonly encountered most is R2R2 Two genes, RHD and RHCE (chromosome 1) code for two main Rh proteins (RHD and RHCE) 2) D type determined by presence/absence of RHD 3) One protein gives both C/c and E/e antigens; combination determined by which alleles of RHCE are present (CE, Ce, cE, or ce) RHAG- chromosome 6 –coexpressor very similar to Rh proteins forms complex with the rh polypeptides
- When Rh-positive red cell samples are typed for the D Ag. It is expected that they will react strongly with anti-D reagent. However, with certain red cells the testing must be carried through the AHG phase to demonstrate the presence of the D Ag. Red cells carrying the weaker D Ag have been referred to as having the D u type. Genetic - The D Ag expressed appear to be complete but few in number. Inheritance of these gene can be tracked from one generation to the next and seen most frequently in black . C transThe Rh Ag on the red cell is normal , but the steric arrangement of the C Ag in relationship to the D Ag appears to interfere with expression of the D Ag. Mosaic- One or more parts of the D Ag are missing Wiener and Unger postulated that the complete D (Rho) Ag had four parts designated Rh A , Rh B , Rh C , Rh D , a lowercase superscript of a, b, c, and d is used to indicate when the corresponding portion (s) of the mosaic is missing. Example, Rh b means the B portion is absent. People with weak D are considered Rh+ and receive Rh+ blood (except mosaics)
- Rh Abs do not bind complement. For complement to be fixed, two IgG molecules must attach in close a proximity on the red cell surface. Red cell destruction due to Rh Abs is primarily extra-vascular. This type of hemolysis classically characterizes a delayed hemolytic transfusion reaction. Produced after exposure of the individual’s immune system to foreign red cells, either through transfusion or pregnancy. Rh Abs often persists in the circulation for years Rh Abs are considered clinically significant , therefore, Ag negative blood must be provided to any patient with a history of Rh Ab sensitization.