الفهرس 
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Abstract
Human red blood cells (RBCs) have numerous cell surface structures that can be recognized as antigens by the immune system of individuals who lack that particular structure.
Blood groups antigens are approximately 302 Ags; were identified &categorized into 29 systems, 5 collections, and 2 series by the international society of blood transfusion (ISBT).
Antibodies to many of these antigens have the potential to be clinically significant; that is, they can facilitate accelerated destruction of red cells carrying the corresponding antigen and these antibodies can persist for several years. It has been recognized that knowledge and understanding of blood groups are essential for transfusion therapy; this is because individuals who lack antigens on their red blood cells can be alloimmunized, if they are exposed to blood expressing the antigen. This might occur with transfusion of blood products or during pregnancy. Antibodies that react with red blood cell antigens can cause problems such as delayed and immediate hemolytic transfusion reactions (HTRs), hemolytic disease of the fetus and newborn (HDFN) and rejection of an allograft which expresses particular blood group antigens.
The ABO blood group system is the most important , and differs from all blood groups in that, the Abs against the ABO system are naturally occurring IgM , that can cause intravascular hemolytic transfusion reactions (IHTRs), which is fatal.
The Rh blood group has become second in importance after the ABO, followed by Kell, Kidd, Duffy and Ss blood group antigens that are also highly immunogenic.
Pre-transfusion compatibility testing requires detection of red cell typing of the donor and Abs detection & identification of the patient’s serum, to assure survival of the transfused red cells to the patient, and to avoid HTRs.
Red cell typing for ABO, Rh & other blood group antigens (Ags) is done by testing the red cells with monospecific Anti-sera using tubes, microplates, or column agglutination technique (CAT) to detect the phenotype of the cells (serological testing).
Now it is possible to determine blood group phenotypes from deoxyribose nucleic acid (DNA). Currently, this technology is generally applied to determining blood groups when suitable red cells are not available, such as fetal testing and blood grouping on multiply transfused patients. Simple DNA-based assays can be used to identify defined Single- nucleotide polymorphisms (SNPs) in genes encoding blood groups (genotyping).
Detection & identification of red cell antibodies are fundamental to transfusion practice and provide information which aids in the selection of suitable blood for transfusion. Identification of an antibody to red cell antigens requires testing the serum against a panel of selected red cell specimens with known antigen composition for the major blood groups, using proper indirect antiglobulin technique (IAT).
Column agglutination techniques (CAT) have resulted in an increased sensitivity in detecting red cell antibodies, as compared with the conventional tube test.
In addition to the value of typing donors for antibody identification panels, DNA analyses are being used to aid in the identification of antibodies.
Clinical bioassays can be used as a functional assessment for the significance of Abs in patients requiring transfusion, also can be used for predicting the severity of hemolytic disease of the fetus and newborn (HDFN); the Antibody-dependent cellular cytotoxicity (ADCC), Monocyte monolayer assay (MMA) and Chemiluminescence’s test (CLT) have all been used for this purpose.
DNA-based blood group typing provides a valuable adjunct not an alternative to traditional methods of pretransfusion testing. Traditional methods for ABO and D typing are likely to continue, and methods for antibody detection and identification will still be required. Theoretically, it is possible to match patient and donor blood group genotypes electronically with the use of gene chip technology. However, this assumes DNA-based methods are totally robust, which they are not because novel mutations arise continually. It also assumes the blood available for transfusion at any given time will match all patients’ blood group phenotypes for all possible polymorphic antigens capable of stimulating clinically significant antibodies, which is unrealistic. Tandem application of DNA-based methodology and existing methods will however provide improvements in the provision of extensively blood group–phenotyped red cells for patients with alloantibodies.