الفهرس 
Chapter (1): ?-ThalassemiaOnly 14 pages are availabe for public view
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Abstract
The differences in human blood groups are due to the presence or absence of certain protein molecules called antigens. 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.
The membrane of each red blood cell contains millions of antigens that are ignored by the immune system. However, when patients receive blood transfusions, their immune systems will attack any donor red blood cells that contain antigens that differ from their self-antigens. This is because individuals who lack antigens on their red blood cells can be alloimmunized, if they are exposed to blood expressing the antigen. That can cause delayed hemolytic transfusion reactions (DHTRs), which is fatal.
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. Red blood cell (RBC) alloimmunization is common in chronic transfused patients, as in beta thalassemia.
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 blood group antigens that are also highly immunogenic.
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).
This study was performed to estimate the frequency of alloimmunization against red cell antigens in transfusion dependent thalassemic patients to identify positive screened patients.
Our study included 200 multitransfused thalassemic patients. They were 111 males and 89 females and were subjected to the following investigations:
ABO grouping and Rh detection
Screening of the patient’s plasma/serum for antibody presence by inducing a reaction between antibodies in patient’s plasma/serum & blood group O cells of known phenotype.
Antibody identification of patients with positive screening to detect the development of new alloantibodies & the type of these antibodies.
18 patients of the 200 patients gave positive results and showed antibodies against the different red cell antigens, with the percentage of alloimmunization to red cell antigens 9%. The antibodies to Kell antigen and to Rh system antigens were detected most frequently which reflects the greater immunogenicity of these red cell antigens.