CLS 3311 Advanced Clinical Immunohematology

1. CLS 3311Advanced Clinical Immunohematology Rh Blood Group System

2. Rh Blood Group System After the A and B antigens the D antigen is the most important red cell antigen in transfusion practice. AABB Technical Manual

3. WHY is D antigen so important? • D antigen is VERY IMMUNOGENIC • >80% of D Negative persons exposed to D Positive blood are expected to develop anti-D antibodies. • Anti-D antibody • RBC Immune (Stimulated) • What characteristics does ‘RBC Immune’ imply about the anti-D antibody?

4. Rh Blood Group System Rh Blood GroupSystemconsists of more than just the D antigen. It also contains other clinically significant antigens including: C, c, E & e.

5. Two highly homologous genes… Two closely linked genes control the expression of ALL Rh antigens Codominant alleles Encode nonglycosylated polypeptides that express Rh antigens Proteins w/o any carbohydrates attached RHD gene – determines the presence of a protein that confers D activity on RBC RHCEgene– determines presence of C, c, E, e antigens; alleles are RHCe, RHCE, RHcE, RHce Current Rh Genetics Theory

6. Schematic diagram of RHCE and RHD genes and proteins. AABB Technical Manual, Figure 14-1, page 298 (Courtesy ME Reid, New York Blood Center)

7. Principle Rh Gene Complexes and Antigens Encoded

8. Rh Nomenclature/Genetics • Bunch of investigators developed their own nomenclatures and theories of inheritance at about the same time…soooo we get to be very familiar with a couple of them and aware of all of them: • Fisher-Race • Weiner • Rosenfeld • ISBT

9. Rh Nomenclature/Genetics Fisher-Race:Genetics/Terminology • These investigators postulated that 3 sets of closely linked genes produced the Rh antigens • Each gene product was an Rh antigen on RBC • Both gene and gene product have same designation. Page 130, Table and Fig 6-1 (Also seen in the following slides) Presents the easiest way to communicate the research and serologic findings

10. Fisher-Race:Genetics/Terminology • Page 129-130 Harmening • Rh phenotype is designated by the presence or absence of Rh antigens: D, C, c, E, e • little d: Indicates the ABSENCE of the D antigen and nothing more. There is NO little d antigen or allele. Many blood bankers today are leaving the ‘d’ out the the nomenclature entirely. • Phenotype example: R1 phenotype is D, C, e • Rh genes are codominant.

11. In the Fish-Race theory theD genecodes for theD antigen. TheC genecodes for theC antigen, etc.

13. Significance of Table 6-1 • Helps us predict the Most Likely Genotype of an individual depending on race. • Example: White person has the D, C, c and e antigens on their red blood cells. I need two haplotypes - one from Mom and one from Dad! • What is the most likely Genotype of this person? • DCe/dce (R1r)

14. Weiner Genetics/Terminology • ONE GENE produced an entity called an agglutinogen: • Each agglutinogen contained a series of 3 factors. Current genetic findings do NOTsupport Weiner’s theory of inheritance. • Figure 6-2, pg. 130 Harmening (next slide) • You will need to be able to interchange between Weiner’s Shorthand DesignationandFisher-Race DCEterminology.

16. Weiner Terminology Rh-Hr Terminology • Table 6-3 and 6-4, page 131 Harmening • Agglutinogen represents entire Fisher-Race haplotype: • Example: R1 represents DCe • Upper case R indicates the presence of D, Lower case r represents the absence of D, designated as ‘d’, etc. • Must become familiar with shorthand

17. This represents both Weiner terminology and genetics. Need to be comfortable with both.

20. Practice, Practice, Practice • Use the preceding table for practice. Cover the last two columns and practice predicting the Most Likely Genotype! • Then you can make your own table and continue the process. You need to be able to predict theMost Likely Genotypefrom common patient Rh antigen typings using antisera for the D, C, c, E & e antigens.

21. Rosenfeld and ISBT • Rosenfeld: Nomenclature based on ‘order of discovery’ or ‘relationship to Rh blood group system’. No genetic relationship with this terminology • ISBT - International Society of Blood Transfusion: The Working Party on Terminology for Red Cell Surface Antigens • Nomenclature that is both ‘eye and machine’ readable. For both people and computers. • Table 6-5, page 132 Compares all nomenclatures

22. Most Probable Genotype • Presumptions reside on Phenotype Frequencies. • We cannot predict a patients Most Likely Genotype without first knowing the Rh Phenotype Frequencies • If RBCs express both C & c or E & e the corresponding genes are present (Heterozygous). If they express only C or c or only E or e the person is assumed to be Homozygous for that gene.

23. Most Likely Genotype • Which antigens are present on RBC? For this example: D, C, c, E antigens 2. Which genes code these antigens? RHD, RHCE, RHcE 3. What haplotypes integrate these antigens? DcE, dcE, DCE, dCE 4. Which are the Most Common? (Remember I need two: one from Dad and one from Mom) DcE and dcE (R2 and r”)

24. Most Likely Genotype • TheMost Likely Genotypeis:DcE/dcE General Rules for Predicting Most Likely Genotype: • Do not CREATE matter. If an antigen is NOT on the RBC don’t add it to your genotype. • Do not DESTROY matter. If an antigen IS on the RBC make sure it is still there when you select the most likely genotype.