Blood Group System Lab -3- PDF

‫جامعة تكريت‬ ‫كلية الطب‬ ‫فرع االحياء المجهرية الطبية‬ ‫م‪.‬م‪.‬جعفر جميل ابراهيم‬ ‫المرحلة الثانية‬ ‫‪Blood Group System‬‬ ‫‪Lab -3-‬‬  ABO Blood Group System The ABO system is the first most important of all blood gr...

‫جامعة تكريت‬ ‫كلية الطب‬ ‫فرع االحياء المجهرية الطبية‬ ‫م‪.‬م‪.‬جعفر جميل ابراهيم‬ ‫المرحلة الثانية‬ ‫‪Blood Group System‬‬ ‫‪Lab -3-‬‬  ABO Blood Group System The ABO system is the first most important of all blood groups in transfusion practice. It is the only blood group system in which individuals have antibodies in their serum to antigens that are absent from their RBCs. This occurs without any exposure to RBCs through transfusion or pregnancy.  ABO Blood Group System Due to the presence of these antibodies, transfusion of an incompatible ABO type may result in immediate lysis of donor RBCs. This produces a very severe, if not fatal, transfusion reaction in the patient.  ABO Blood Group System The A and B antigens are not fully developed at birth. As a result, reactions of newborn RBCs with ABO reagent antisera are frequently weaker than reactions with adult cells. The expression of A and B antigens on the RBCs is fully developed by 2 to 4 years of age and remains constant.  ABO Antibodies Individuals normally produce antibodies directed against the A and/or B antigen(s) absent from their RBCs. These antibodies have been described as naturally occurring because they are produced without any previous exposure to RBCs.  ABO Antibodies The ABO antibodies are predominantly IgM. The production of ABO antibodies is initiated at birth, but titers are too low for detection until the individual is 3-6 months of age.  ABO Antibodies ABO antibodies can cause rapid intravascular hemolysis if the wrong ABO group is transfused; this can result in the patient dying.  Routine ABO Testing Forward grouping is defined as using of antisera (anti-A, anti-B) to detect antigens on an individual's RBCs. Reverse grouping is defined as using of reagent RBCs (A1 and B cells) to detect ABO antibodies in the patient's serum.  Rh Blood Group System Rh is the second most important blood group system in transfusion, as the Rh system antigens are very immunogenic. Unlike ABO antibodies that are naturally found in individuals who lack the corresponding antigen, Rh antibodies are produced only after exposure to foreign red blood cells.  Rh Blood Group System Rh-positive indicates that an individual's red blood cells possess the Rh antigen (D antigen) on their red blood cells. Rh-negative indicates that the red blood cells lack the D antigen.  Rh- antigens Individuals are often called Rh-positive if they have the D antigen and Rh-negative if they lack D. Approximately 85% of people are D-positive. Rh antigens are well developed early in fetal life.  Rh- antibodies Most Rh antibodies are IgG and react optimally at 37°C or after anti-globulin testing (indirect Coombs's test). Rh antibodies are usually produced following exposure of the individual to foreign RBCs, through either transfusion or pregnancy.  Rh- antibodies Rh antigens are highly immunogenic; the D antigen is the most potent. Exposure to ≥ 0.1 mL of Rh D-positive RBCs can stimulate antibody production in an Rh D- negative person. Rh antibodies often persist in the circulation for years.  Rh- antibodies Because Rh antibodies are primarily IgG and can traverse the placenta and because Rh antigens are well developed early in fetal life, Rh antibodies formed by Rh-negative pregnant women cross the placenta and may coat fetal RBCs that carry the antigen. This can result in hemolytic disease of the newborn (HDN) in which the coated fetal cells are destroyed.