Hematology branch that studies and analyzes the immunological characteristics of blood.
The ABO system was the first system blood group identified and remains today the most important antigenic system for transfusion practice. In fact, the ABO compatibility between donor and recipient is the basic requirement for each transfusion. Normally each subject possesses in their serum antibody capable of recognizing the antigens of the AB system that are not present on the surface of their red blood cells. This complementary relationship allows to perform the investigation for the determination of the ABO group on both the serum and the red blood cells.
Since the formation of blood group antibodies normally begins only after birth, you can not determine the ABO group with indirect test on the serum of infants or children under the age of 4-6 months. Also in the serum of newborns can be present anti-A or anti-B IgG passively acquired from the mother to pass the placenta. The production of anti-A and anti-B began in the early months of life and increases in the first 5 or 6 years after which remains more or less constant until old age and then decreases in the elderly.
The subjects able to achieve an immune response react to antigenic stimuli (type A and B) producing antibodies directed against those which do not possess specificity ABO. Thus in the serum of subjects of group O and group B are formed antibodies anti-A and those of group O and group A are formed antibodies anti-B. The subjects of group AB, owning both antigens do not form any antibody.
The terms “Rh-positive” and “Rh-negative” refer to the presence or absence of an antigen on the erythrocyte membrane universally defined antigen D. It is, after the A and B antigens, the most important antigen for the red cell transfusion practice. Unlike the ABO system those who do not have the D antigen as a rule do not have the corresponding antibody, anti-D serum. The formation of the antibody is due to exposure to red blood cells that have antigen.
Such exposure can be realized as a result of pregnancy or blood transfusion. Subsequent family studies have shown that the presence of the antigen on the red blood cells is genetically determined and that the gene is autosomal dominant. The gene “Rh” is located on chromosome 1.
The adoption of more sophisticated tests led to the detection of antibodies that recognize antigens and show a clear correlation with the antigen D. The 4 antigens discovered after the D antigen, were referred to as C, E, c and e. The association of these antigens suggests that the immunogenicity Rh is linked to molecules of the surface equipped with several antigenic determinants. In some of these molecules with antigenic activity, this is the D antigen, while it is absent in others. The composition of these configurations antigen is genetically determined. For the 5 major antigens, known involvement of a single gene in determining both the production of the D antigen and C, c, E and e. While we have identified and studied several variations and combinations, these five antigens and their antibodies, form the foundation of the Rh system.