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2. Introduction to immunohaematology. BY Dr:Maha AL-Sedik. Objectives: 1- Rh blood group system. 2- Antigen and antibody of each blood group type. 3- Detection of the Rh blood group. 4- Importance of Rh blood group system. 5- Antihuman globulin ( Coombs , ) test.
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2 Introduction to immunohaematology BY Dr:Maha AL-Sedik
Objectives: 1- Rh blood group system. 2- Antigen and antibody of each blood group type. 3- Detection of the Rhblood group. 4- Importance of Rh blood group system. 5- Antihuman globulin ( Coombs, ) test.
Rh blood group system: As some red blood cells have an additional antigen (known as the RhD antigen), there is a further type of classification. If the red blood cells contain this antigen then they are classed as RhD +ve, and if they don't, are classed as RhD -ve. Anti Rh gene is of IgG type.
This means that there are eight main blood types, these are: • A positive (A+) • A negative (A-) • B positive (B+) • B negative (B-) • AB positive (AB+) • AB negative (AB-) • O positive (O+) • O negative (O-) • There are 2 major subgroups of group A : A1 : 80% & A2 :20%
Importance of Rh blood grouping: • Haemolytic transfusion reaction in case of Rh mismatched blood transfusion. • Acute graft rejection in case of Rh incompatible solid organ transplantation. • Haemolysis of donor red cells following Rh incompatible bone marrow transplantation. • Rh antibody can cause haemolytic disease of newborn. • Medicolegal importance.
Antihuman globulin (coombs' test) Detection of non-agglutinating Ab , especially IgG or complement components (C3d) affixed to RBCs in vivo or in vitro.
Direct antiglobulin test (DAT): detection of sensitization of RBC s (coated with Abs and/or complement components) in vivo. • Indirect antiglobulin test (IDAT): detection of sensitization of RBCs in vitro.
Indirect Coombs test (Indirect Antiglobulin test): to detect presence of IgG or complment in patients serum. Indications: • To check whether an Rh-negative women (married to Rh-positive husband) has developed Anti Rh-antibodies. • Pre-transfusion of Rh positive blood to Rh negative recipient.
Direct Coombs test (direct Antiglobulin test): The direct antiglobulin test (DAT) detects sensitized red cells with IgG and/or complement in vivo. Indications: • Hemolytic transfusion reaction. • Hemolytic disease of the newborn (also known as HDN or erythroblastosis fetalis).