BB LAB

• An immunogen is an antigen that provokes the immune response. Not all antigens are immunogens.
• Immunohematology


  Study of blood group antigens and antibodies
• General properties of antibodies

  • Immunoglobulin is a glycoprotein secreted by plasma cells that binds to specific epitopes on antigenic substances
  • Five classifications: IgG, IgA, IgM, IgD
• General properties of antigens


  • Foreign molecules that bind specifically to an antibody or a T-cell receptor
  • Located on viruses, bacteria, fungi, protozoa, blood cells, organs, and tissues
  • Allogeneic cells or tissues from a genetically different individual
  • Autologous cells or tissue from self
  • Antigenic determinants or epitopes are sites on an antigen that are recognized and bound by a particular antibody or T-cell receptor
  • Immunogen is an antigen capable of eliciting an immune response
• Factors contributing to immunogenicity

  • Molecular size
  • Chemical composition and complexity of the antigen
  • Conformation
  • Accessibility
  • Charge
  • Digestibility
  • Degree of Foreignness
  • Dosage and antigen density
  • Route of administration
• Blood Banking


  Process of collecting, separating, and storing blood
• Immunoglobulin M (IgM)


  • Concentration: 6% of the immunoglobulin pool
  • Exists in both monomeric and polymeric forms (as pentamers)
  • React best at room temperature or lower
  • Associated with intravascular hemolysis
  • Antigen-antibody complexes can be detected in immediate-spin
• Antibodies


  Immunoglobulins that bind antigens, fix complement, facilitate phagocytosis, and neutralize toxic substances in the circulation
• Immune antibodies are found in the serum of individuals who have been transfused or pregnant
• Immunoglobulin G (IgG)


  • Occurs only as monomers
  • Major immunoglobulin in normal serum (80%)
  • Bivalent (possesses two antigen-combining sites)
  • Clinically significant antibodies that react at body temperature (37°C)
  • Important in transfusion medicine and Hemolytic Disease of the Fetus and Newborn (HDFN)
  • Associated with extravascular hemolysis
  • Has subclasses: IgG1, IgG2, IgG3, and IgG4
  • Antigen-antibody complexes can be viewed with the use of antiglobulin test
• All antibodies are Ig but not all Ig are antibodies
• Naturally occurring antibodies are found in the serum of individuals who have never been previously exposed to RBC antigens by transfusion, injection, or pregnancy
• Introduction of antigen to the body increases immunogenicity
• Immunoglobulin A (IgA)


  • Serum IgA is found in both monomeric and polymeric forms
  • Secretory IgA is usually found in the mucosal tissues of the body
  • Importance in immunohematology: 30% of anti-A and anti-B antibodies are of the IgA class, Anti-IgA antibodies can cause severe anaphylaxis, Increases the effect of IgG-induced RBC hemolysis
• IgG is considered non-agglutinating
• Immunoglobulins in serum

  • IgG
  • IgA
  • IgM
  • IgD
  • IgE
• Unexpected Antibodies are also called irregular or atypical antibodies
• Unexpected Antibodies may be able to hemolyze, agglutinate, or sensitize RBCs
• Autoantibodies may be Pan- or polyagglutinins, which are autoantibodies that do not have a detectable specificity
• Red cell antibodies are molecules in the plasma or serum
• Alloantibodies are produced after exposure to genetically different, or nonself antigens such as different RBC antigens after transfusion
• Unexpected Antibodies include all red cell antibodies other than naturally occurring anti-A and anti-B antibodies (ABO system)
• Sources of Antigen and Antibody for testing in agglutination reactions for blood bank tests

  • Antigen: Reagent red cells, Patient or donor red cells; Antibody: Commercial Antisera, Patient or donor serum/plasma
• Basic procedures in Immunohematology involve the source of antibody + source of antigen leading to an Ag-Ab reaction
• Autoantibodies are produced in response to self-antigens and can react at different temperatures (warm or cold autoantibodies)
• Unexpected Antibodies may be either isotype IgM or IgG (rarely both)
• Most common immune antibodies encountered react with antigens of: Rh, Kell, Duffy, Kidd, and Ss blood group systems
• Routine testing procedures in the Immunohematology laboratory

  ABO/D typing (forward grouping), ABO serum (reverse grouping), Antibody screen, Antibody identification
• Red cell antigens are located on the red cells, part of the cell membrane or protrude from the cell membrane
• Ideal reagent antibody product

  • Contains a concentrated suspension of highly specific, well-characterized, uniformly reactive immunoglobulin molecules
• Monoclonal antibody reagents

  • Made from single clone of B cells that secrete antibodies capable of recognizing one specific epitope of the immunized antigen
  • Monoclonal antibodies are manufactured in vitro using hybridoma technology
  • Hybridomas - hybrid cells formed by the fusion of myeloma cells and antibody-producing cells; used in the production of monoclonal antibodies
• Monoclonal antibody production

  • has multiple specificity
  • Leterogenous group of ab
  • highly specific from the spleen
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• Blood banking reagents

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• Commercially prepared antibody reagents

  • Polyclonal antibody-based products - produced from several different clones of B cells that secrete antibodies of different specificities
  • Monoclonal antibody-based products - produced from single clones of B cells that secrete antibodies of the same specificity
• Examples of monoclonal antibodies


  • Anti-A
  • Anti-B
  • Anti-A,B
  • Anti-C
  • Anti-E
  • Anti-c
  • Anti-e
  • Anti-IgG
  • Anti-C3d
  • Other blood group system antibodies
• Polyclonal antibody reagents

  • Made from several different clones of B cells that secrete antibodies specific for multiple epitopes of the injected antigen
  • A heterogenous population of antibodies
  • Examples of polyclonal antiserum produced for blood bank testing are known as antihuman globulin (AHG) reagents
• Blood banking reagents

  • Anti-A
  • Anti-B
  • Anti-D
  • Anti-C
  • Anti-E
  • Anti-c
  • Anti-e
  • Anti-IgG
  • Anti-C3d
  • Other blood group system antibodies
• Low protein content in monoclonal antibodies can lead to oversensitivity
• Antiglobulin reagents contain both anti-IgG and anti-complement antibodies
• Monoclonal antibody reagents produce large quantities of the desired antibody with lot-to-lot consistency of a single specificity