Nada Mohamed Ahmed, MD, MT (ASCP)i

OBJECTIVES

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

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 Kollam

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

Rh BLOOD GROUP SYSTEM Weak D Antigen (D u ) 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

Rh BLOOD GROUP SYSTEM Presence of D = presence of Rh o factor  Rh (+) Absence of D  Rh (-) A person is grouped as Rhesus (Rh) positive or negative based on the presence or absence of antigen D Rh 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

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.

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.....

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.

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.

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.

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

Rh Groups: Fisher-Race Anti-e Anti-C Anti-D genes linkedclosely- e C D AbAgChromosomee C D 5 major antigens: D, C, E, c and e 14

Rh Groups: Weiner Rh 1 Rh 1 hr” Anti- hr’ hr’ Anti-rh”rh” Anti-rh’rh’ Anti-RhoRhoAbAgCHROMOSOME R1R1R1R1 single gene Anti- hr” 5 major antigens: Rh o, rh’, rh”, hr’, hr” 15

R  D r  no D 1 and ‘  C 2 and “  E Example: DcE  R 2 r”  dcE Written in shorthand

Rh BLOOD GROUP SYSTEM Testing for Rh o (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

Slide Test Method Modified Tube Test Method Du Typing Using Indirect Anti- Globulin Test (IAT)