Rh Blood Group System DR MOHAMMED H SAIEMALDAHR

Rh Blood Group System DR. MOHAMMED H SAIEMALDAHR BB Faculty of Applied Medical Sciences MED TECH DEP drmsaiem

Rh Blood Group System The term Rh refers not only to a specific red cell antigen but also to complex blood group system that is currently comprised on more than 50 different antigenic specificities. History of the Rh System Levine and Stetson described a hemolytic transfusion reaction in an obstetric patient following delivery of stillborn infant. The women required transfusion. Her husband, who had the same ABO type, was selected as her donor, after transfusion the recipient, demonstrated the classic symptoms of acute hemo]ytic transfusion reaction. drmsaiem

Rh Blood Group System 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. drmsaiem

Rh Blood Group System Landsteiner and Wiener reported on an antibody by guinea pigs and rabbits when they were transfused with rhesus monkey red cells. This antibody which agglutinated 85% of human red cells was named Rh. The name Rh was retained for the human produced antibody. Anti-rhesus formed by the animals was renamed anti-LW (Landsteiner and Wiener). drmsaiem

Rh Blood Group System Nomenclature of the Rh System The terminology used to describe the Rh system is derived from 4 sets of investigators. Two of the terminologies are based on the postulated genetic mechanisms of the Rh system. 3 rd terminology describes only the presence or absence of a given antigen. 4 th is result of the effort of the International Society of Blood Transfusion (ISBT) Working Party on Terminology for Red cell Surface antigens. drmsaiem

Rh Blood Group System Fisher-Race (DCE terminology) In the early 1940 s, Fisher and Race were investigating the antigens found on human red cell including the newly defined Rh antigen. Thy postulated that the antigens from the system were produced by 3 closely linked sets of alleles. Each gene was responsible for producing a product (Ag) on the red cell surface. drmsaiem

Rh Blood Group System Each antigen (Ag) and corresponding gene were given the same letter designation. Fisher and Race named the antigens of the system D, d, C, c, E, and e. To date NO (d ) antigen has been found, and it is considered an amorph (silent allele) or the absence of D antigen. The phenotype (blood type observed during testing) of a given red cells is define by the presence or absence of D, C, c, E, and e. drmsaiem

Rh Blood Group System According to the Fisher-Race proposal, each person inherits a set of Rh genes from each parent (one D, or d, one C or c, and one E or e). Rh genes are co-dominant, each inherited gene express its corresponding antigen on the red cell. The combination of maternal and paternal haplotypes (Possessing half the normal # of chromosome found on the cell) determines one’s genotype (the Rh gene inherited from each parent) and dictates one’s phenotype (the antigens expressed on the red cell that can be detected serologically). drmsaiem

Rh Blood Group System An individual’s Rh phenotype is reported as DCE because Fisher-Race postulated that the C/c locus is lies between D/d and E/e loci. It is essential to remember that d doesn’t represent an antigen but simply the absence of the D antigen. C, c, E, e represent actual Ags recognized by specific antibodies. drmsaiem

Rh Blood Group System 2 - Wiener (The Rh-Hr terminology) 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) drmsaiem

Rh Blood Group System Agglutinogen Rh gene Red cell surface Factor Rh 0 Factor hr′ Factor hr″ drmsaiem RH 0 hr ′ hr ″

Rh Blood Group System Wiener (The Rh-Hr terminology) Fisher-Race nomenclature may be converted to Wiener nomenclature and vice versa. It is important to remember that an agglutinogen in the Wiener nomenclature actually represent the presence of a single haplotype composed of three different antigens. R= D antigen r = absence of the D antigen (d). C= indicated by 1 or a single ( ′ ) c= when there is no 1 or (′) E=is indicated by 2 or ( ″ ) e= there is no 2 or ( ″ ) drmsaiem

Rh Blood Group System Example R 1 = DC e R 0 =Dce E=is indicated by 2 or ( ″ ) Example R 2=Dc. E r ′ = d Ce e= there is no 2 or ( ″) r″ =dc. E When both C and E are present the letter Z or Y is used. RZ=DCE r. Y=d. CE R 1 r =DCe/dce r′r =d. Ce/dce drmsaiem

Rh Blood Group System (Wiener Rh) When referring to the Rh Ag (factor) in wiener nomenclature the single prime ( ' ) refers to either C or c. The double prime ( ″ ) refers to either E or e. If the r precedes the h ( rh′ or rh″ ) we are referring to C or E Ags respectively. When the h precedes the r we are referring to either c ( hr′ ) or e ( hr″ ) Ags. Rho = D There is no designation for the absence of D Ag. drmsaiem

Rh Blood Group System Rosenfield (Alpha numeric terminology) In 1960 s 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. drmsaiem

Rosenfield v A minus ( - ) sign preceding a number designated the absence of the Ag. v If Ag has not been typed for, its number will not appear in the sequence. v D is assigned =Rh 1 E=Rh 3 c =Rh 4 C=Rh 2 e = Rh 5 v For cell that typed D+ C+ E+ c- e-, the Rosenfield designation is Rh: 1, 2, 3, -4, -5. drmsaiem

Rosenfield If the sample was not tested for e, the designation would be Rh: 1, 2, 3, -4. All Rh system antigens have been assigned a number. drmsaiem

International Society of Blood Transfusion Numeric terminology They adapted a six digit number for each blood group. The first three number represent the system and the remaining three represent the antigenic specificity. The number 004 was assigned to the Rh blood group system, then each antigen assigned to the Rh system was given a unique number to complete the six digit computer number. drmsaiem

Biochemistry of Rh Antigens. Understanding the results of gene action The final result of gene action in red cell group is the production of the biochemical structure. Rh system is a non-glycosylated protein this mean that, No carbohydrates attached to the protein Rh Ags are transmembrane polypeptide (integral part of the red cell membrane) D associated protein is linked to the membrane skeleton. drmsaiem

Biochemistry of Rh Antigens. The number of D Ag sites, measured on a variety of Rh phenotype # of D antigen sites R 1 r 990, 0 -146, 00 R 0 r 120, 00 -200, 00 R 2 r 140, 00 -166, 00 R 1 R 1 145, 00 -193, 00 R 1 R 2 230, 00 -310, 00 R 2 R 2 158, 00 -333, 00 D-- 110, 000 -202, 000 drmsaiem

Biochemistry of Rh Antigens. The greatest number of D Ag site are on cells of the rare Rh phenotype D --. D-- cell carry only D Ag and completely lack C c and E e. R 2 R 2 cells possess the largest number of D Ag sites. drmsaiem

Detection of Rh Antibodies and Antigens v Are Ig. G, react optimally at 37 o. C or following the addition of antiglobulin reagent v Produced after exposure of the individual’s immune system to foreign red cells, either through transfusion or pregnancy. v Rh Abs often persists in the circulation for years v Rh Abs are considered clinically significant, therefore, Ag negative blood must be provided to any patient with a history of Rh Ab sensitization. drmsaiem

Detection of Rh antibodies and Antigens Rh Abs do not bind complement. For complement to be fixed, two Ig. G molecules must attach in close a proximity on the red cell surface. Red cell destruction due to Rh Abs is primarily extravascular. This type of hemolysis classically characterizes a delayed hemolytic transfusion reaction. drmsaiem

Rh Antigens Rh antigens are highly immunogenic, the D antigen is most potent D c E C e Highly Rarely Immunogenic v Exposure to less than 1 ml of Rh positive red cells can stimulate Ab production in an Rh negative person. drmsaiem

Determination of D Status Is essential when test donor blood sample. Blood considered Rh positive if either the D or Du test is positive If any donor blood sample that types Rho(D) negative by either slide or rapid method must be tested further by indirect anti-globulin test (IDAT). If both test results are negative, the donor sample is considered Rh negative. drmsaiem

Determination of Du Status There are instance when an accurate Rh type can not be determined through routine testing v 1 - If the new-born’s cell are coated with maternal Ig. G anti-D in utero, very few D Ag sites will be available to react with reagent anti-D. v Elution of the sensitizing Ab (removing the Ab) and identifying it as anti-D will verify that the infant’s red cell are D positive v 2 - Warm autoimmune hemolytic anemia, Abs are directed against the patient’s own red cell and react as though they are Rh specific. drmsaiem

Variation of the Rho (D) Antigen Weak D overview 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 Du type. drmsaiem

Variation of the Rho (D) Antigen Three different mechanisms have been described that can explain the weakened expression of the D Ag. Genetic weak D Inheritance of D genes that code for a weakened expression of the D Ag. 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. drmsaiem

Variation of the Rho (D) Antigen C Trans (a position effect or gene interaction effect) The 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. This interference with D expression does not occur when the C gene is inherited in the cis (The location of two or more genes on the same chromosome of a homologius pair). Family study can be distinguish which type of weakened D Ag is being demonstrated. drmsaiem

Variation of the Rho (D) Antigen D 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, Rhb means the B portion is absent. drmsaiem

Rh Reagents v Coomb’s cells (C. C) Control cellular used when AHG test is negative. To confirm that washing has been adequate and the antiglobulin reagent is reactive v Control Cell A group O Rh positive donor’s sample is mixed with 1: 10 dilution of reagent anti-D and allowed to incubate. After sensitization of RBC, they are washed with saline and suspended to a 50% RBC suspension These sensitized RBCs then used to confirm the anti-Ig. G activity of the AHG. drmsaiem

Rh Reagents v Coomb’s cells (C. C) They can be used to ensure that AHG test with neg results are not false neg because of inactivation of the AHG reagent. When AHG test is neg , they should be free AHG reagent in the test tube When the CC are added, the free AHG in the test should cause agglutination of the sensitized RBCs. v This positive reaction is a mixed field in nature because; half of RBCs in the mixture lack Ig. G on their surface and are free cells v 2 nd half of RBCs have Ig. G (CC) and are agglutinated drmsaiem