IH LE 1

• Immunohematology is related to blood banking, transfusion medicine, or transfusion laboratory
• The course deals with concepts and principles of red cell antigen systems and the application of specific blood group antigens and antibodies to compatibility testing
• Hematology involves reactions with red cells and not any other cells or tissues of the body
• Immunology involves antigens and antibodies
• Blood bank is the only part of the laboratory that deals with the treatment of patients through the use of blood and blood products known as Transfusion Medicine
• Errors in the blood bank section can lead to more deaths than errors in other lab sections
• Blood bank is critical as it caters to both patients/recipients and donors
• Majority of blood bank testing focuses on the prevention, detection, and identification of blood group antibodies and typing of red blood cell antigens
• In most transfusion lab testing, hemagglutination reactions are the major technique used for analyzing blood group antigen-antibody responses and typing for ABO, Rh, and other blood group antigens
• Agglutination develops in two stages: Sensitization and Lattice Formation
• Sensitization is the first stage where antigen binding to the antibody occurs
• Antibodies attach to the antigen on the red blood cell membrane during sensitization
• RBCs coated with antibodies during sensitization are called sensitized RBCs
• Lattice Formation is the second stage where a lattice-type structure composed of multiple antigen-antibody bridges between RBC antigens and antibodies is formed
• Zeta potential is the natural repulsive effect of red blood cells to each other due to their net negative charge
• Negative charges on RBCs repel each other, making it challenging for lattice formation or cross-linking of antigen-antibody complexes
• The most efficient agglutinator among all immunoglobulins is IgM
• IgG is the smallest immunoglobulin class while IgM is the largest
• IgM is the best antibody for agglutination due to its size and structure
• IgM is made up of five structural units and can reach antigenic sites up to 35 nm apart, while IgG is made up of a single structural unit and can only attach up to 14 nm antigenic sites
• Antibody forms a cross-link between two RBCs
• True agglutination is unstained under the microscope
• Prepared using a wet mount with the microscope diaphragm half closed
• Staining like the Wright stain causes RBCs to clump together
• Stained
• Anti-A, Anti-B, Anti-D of the Rh blood group, and negative control
• Agglutination occurs in Anti-A due to the presence of A antigen
• Agglutination occurs when both antigen and antibody are present
• No agglutination in Anti-B due to absence of B antigen
• Agglutination occurs in Anti-D for Rh blood group
• Negative control helps differentiate true positive or negative results
• Gel Card Agglutination
• Cell settling at the bottom indicates a negative result, on top indicates agglutination
• Gel is porous, allowing non-agglutinated cells to pass through after centrifugation
• Hemolysis indicates a positive result in Ag-Ab reaction
• Complement fixation or activation occurs, part of humoral immunity
• Hemolysis is invalid if sample is hemolyzed prior to testing
• Hemolysis occurs when complement activating antibody attaches to an antigen
• Agglutination is the endpoint for most in vitro tests involving erythrocyte Ags and blood group Abs
• Optimal concentrations of Ag and Ab are necessary for agglutination reactions