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The Inducible System: Antigens
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Still, tissues cannot be freely transferred from one member of a species to another member of the same species. Molecules of one individual of a species which are antigenic in another member of the same species are called isoantigens and the antibodies that are produced are called isoantibodies. A well-studied example of such antigens is the ABO blood group system in humans. These blood groups are defined by the presence or absence of different glycoproteins on the surfaces of red blood cells. Groups A and B differ only in one sugar: group A glycoproteins have a terminal N-acetyl galactosamine amine and group B glycoproteins have galactos-amine. The genes thai determine these blood groups encode the transferases responsible for synthesis of the oligosaccharide portion of the glycoprotein. If an Individ ual lacks the gene for the A transferase, he will develop antibodies to A in his blood serum from exposure to similar bacterial antigenic determinants. If the blood of this individual is transfused to someone with type A blood, these isoantibodies will clump and destroy the red blood cells of the recipient. For this reason, careful blood typing is standard procedure before blood transfusion.
Inherited Defects in Immune Defenses Leading to Pulmonary Disease
Published in Stephen D. Litwin, Genetic Determinants of Pulmonary Disease, 2020
The structural differences between Ig classes, subclasses (Ig heavy chain), and types (Ig light chain) are associated with different roles in immune defense. This can be illustrated by the Ig classes. IgG is the major opsonin, while IgM is more effective in complement fixation. IgA predominates in local immune defenses, IgE in allergic responses. IgD is probably critical in cellular regulation of Ig production. There also are differences within the IgG subclasses (IgGl-4); IgGl and IgG3 can fix complement more effectively than IgG2, while IgG4 does not fix complement at all. Only IgG2 mediates passive cutaneous anaphylaxis. Certain "autoantibodies" are relatively restricted to IgG subclasses. The immune response to exogenous antigens and most microorganisms is polyclonal; all major Ig classes, subclasses, and light chain types are usually represented in the specific antibody response. However, restricted antibody responses have been documented in humans for Rh isoantibodies [17], for polysaccharide antigen antibodies [18], and for tetanus and pertussis antibody [19].
Immune Hemolytic Anemias
Published in Harold R. Schumacher, William A. Rock, Sanford A. Stass, Handbook of Hematologic Pathology, 2019
Joseph P. Yoe, Ronald A. Sacher
IgG antibodies are much smaller than IgM antibodies. Clearance of IgG-coated erythrocyte is more complex than that of IgM-sensitized cells and usually not through the complement-mediated intravascular lysis of sensitized erythrocytes. Since the IgG antibodies occupy antigenic sites on the red cell, they may block agglutination of additional RBCs by IgM antibodies, thus the name “blocking” or “incomplete” antibodies. Although the IgG antibody molecule has two binding sites, generally they are unable to react completely with RBCs suspended in saline because of the distance between RBCs imposed by the negative surface charge. Therefore, the IgG antibodies coat the surface of the RBCs but do not cause actual agglutination in saline. Examples of IgG antibodies include: Rh isoantibodies that form after repeated exposure to Rh antigenWarm autoantibodies of idiopathic or secondary acquired autoimmune hemolytic anemiaMost drug-related antibodies
Forward and reverse typing discrepancy and crossmatch incompatibility of ABO blood groups: cause analysis and treatment
Published in Hematology, 2023
Hongmei Qiu, Xuechun Wang, Yan Shao
We performed positive and negative blood group typing, antibody screening, and the selection of ABO and Rh homologous blood for cross matching prior to the transfusions (Flowchart 1). Forward and reverse blood group typing and Rh(D) blood group identification method: Microlab STAR IVD Automatic Blood Analyzer. Irregular antibody screening was carried out using the normal saline method, coacylamine method, and anti-human globulin method. We followed the manufacturer’s instructions provided in the package inserts and National Clinical Laboratory Procedures [2] for the other tests, including antiglobulin test, absorption test, and diffusion test. Saline tube test, microcolumn agglutination, and polybrene were adopted for crossmatch tests, and we followed the manufacturer’s instructions provided in the package inserts. Antibody subtypes were identified with a heat release test, while isoantibodies and autoantibodies were detected with an acid release test. The flowchart about blood crossmatch incompatibility test was shown in Figure 1.