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Transcript
Blood group serology The Nature of Blood The term blood refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substances. The fluid portion of blood is called plasma. It is composed primarily of w ater and accounts for 55% of blood content. Blood Solids: Suspended in the plasma are these solid (cells) materials: Red blood cells or erythrocytes White blood cells or leukocytes Platelets Serum The liquid that separates from the blood when a clot is formed. Blood clots when fibrin (a protein) traps and enmeshes the red blood cells. Blood serology includes the study of: Red Blood Cells Antigens. White Blood Cells Antigens. Platelet Antigens. Antibodies in the serum. Compatibility studies for transfusion purposes. Antigen: A substance, foreign to the body that stimulates the production of antibodies by the immune system. Were originally defined as, non-self molecules which bound specifically to antibodies. Antigens which induce adaptive immunity are called immunogens. All immunogens are antigens, and are usually called antigens unless their ability to induce an immune response is being changed. Some antigens, called haptens, are not immunogenic unless they are covalently linked to immunogenic carriers (usually proteins). Hapten: Small foreign molecule that is not antigenic. Must be coupled to a carrier molecule to be antigenic. Once antibodies are formed they will recognize hapten. The antigen bound by a unique antibody in a specific part which is called an epitope. Most proteins have several epitopes that are recognized by different B cells and induce a polyclonal antibody response. Most are proteins or large polysaccharides from a foreign organism. Microbes: Capsules, cell walls, toxins, viral capsids, flagella, etc. Non-microbes: Pollen, egg white, red blood cell surface molecules, serum proteins, and surface molecules from transplanted tissue. Lipids and nucleic acids are only antigenic when combined with proteins or polysaccharides. Molecular weight of 10,000 or higher. Epitope: Small part of an antigen that interacts with an antibody. Any given antigen may have several epitopes. Each epitope is recognized by a different antibody. There are two types of immune response: Negative Ag response: Once Ag in the body, there is no response either humeral or cellular immunity " non responsive''. e.g. if a patient accepted a given kidney. Positive Ag response. Antibody A protein (immunoglobulin) produced by a B-cell that binds to a specific foreign antigen in the blood or body fluids. This leads to attack by the immune system. Belong to a group of serum proteins called immunoglobulins (Igs). Proteins that recognize and bind to a particular antigen with very high specificity. Made in response to exposure to the antigen. One virus or microbe may have several antigenic determinant sites, to which different antibodies may bind. Each antibody has at least two identical sites that bind antigen: Antigen binding sites. Types of Ab: Allo Abs: Produced when the Ag is from the same species, e.g. from human to human. Auto Ab: Ag is a self Ag; stimulate production of Auto-Ab. e.g. immune haemolytic anaemias. Hetero Ab: Ag from a different species, e.g. from a camel to human Brief Introduction to Antibody Structure The Ab takes a flexible Y-shaped molecule; it consists of four polypeptides chains linked by disulphide bonds: 2 identical light chains "L" which is called kappa. 2 identical heavy chains "H" which is called lambda. Variable Regions: Two sections at the end of Y’s arms. Contain the antigen binding sites (Fab). Identical on the same antibody, but vary from one antibody to another. Constant Regions: Stem of monomer and lower parts of Y arms. Fc region: Stem of monomer only. Important because they can bind to complement or cells. Heavy chains have five different isotypes which divide the Igs into five different classes, each with different effector functions (in humans IgG1-4, IgA1-2, IgD, IgM, IgE). Ab classes: Antibodies are grouped into one of five immunoglobulin classes: 1- IgA (IgA1-2): alpha Structure: Dimer Percentage serum antibodies: 10-15% Location: Secretions (tears, saliva, intestine, milk), blood and lymph. Half-life in serum: 6 days Complement Fixation: No Placental Transfer: No Known Functions: Localized protection of mucosal surfaces. Provides immunity to infant digestive tract. Called as secretory IgA (sIgA). IgG (IgG1-4): Gamma. The most common serum antibody. It can pass from mother to fetus during pregnancy, and diffuse across mucosal surfaces, the molecular weight is 160.000 D. IgG is also present in vaginal secretions, in higher concentrations than sIgA. Structure: Monomer Percentage serum antibodies: 80% Location: Blood, lymph, intestine Half-life in serum: 23 days Complement Fixation: Yes Placental Transfer: Yes Known Functions: Enhances phagocytosis, neutralizes toxins and viruses, protects fetus and newborn. IgM: Mew. Heavy molecular weight 1000.000. Structure: Pentamer Percentage serum antibodies: 5-10% Location: Blood, lymph, B cell surface (monomer) Half-life in serum: 5 days Complement Fixation: Yes Placental Transfer: No Known Functions: First antibodies produced during an infection, before IgG. Effective against microbes and agglutinating antigens. IgD: Delta Structure: Monomer Percentage serum antibodies: 0.2% Location: B-cell surface, blood, and lymph Half-life in serum: 3 days Complement Fixation: No Placental Transfer: No Known Functions: In serum function is unknown. On B cell surface, initiate immune response. IgE: Epsilon. Structure: Monomer Percentage serum antibodies: 0.002% Location: Bound to mast cells and basophils throughout body. Blood. Half-life in serum: 2 days Complement Fixation: No Placental Transfer: No Known Functions: Allergic reactions, possibly lysis of worms. Antigen-Antibody Reaction The interaction between the Ag and its specific Ab to form a complex is mediated by multiple bonds between the ADS and the ABS. these bonds include: Hydrogen bonding. Electrostatic bonds. Vander waals bonding. Hydrophobic bonding. -Hydrogen bonding results from formation of hydrogen bridges between appropriate atoms. - The electrostatic forces results from attraction between oppositely charged groups. - Vander Waals bonds generated by the interaction between electron clouds. - The Hydrophobic bonds may contribute to about half of the total attractive forces between the Ag and Ab. These bonds operate over a short distance; therefore the ADS must closely approach to ABS before interaction can occur. Notes: The Ag-Ab reaction is enhanced in presence of electrolytes. The Ag-Ab reactions are characterized by: 1) Being highly specific. 2) Depending in the non-covalent bonds; therefore they are mostly reversible. Consequences of Antigen-Antibody Binding: Antigen-Antibody Complex: Formed when an antibody binds to an antigen that it recognizes. Affinity: A measure of binding strength. 1. Agglutination: 2. Opsonization: 3. Neutralization: 4. Antibody-dependent cell-mediated cytotoxicity: 5. Complement Activation: 1. Agglutination: Antibodies cause antigens (microbes) to clump together. IgM is more effective that IgG. Hemagglutination: Agglutination of red blood cells. Used to determine ABO blood types and to detect influenza and measles viruses. 2. Opsonization: Antigen (microbe) is covered with antibodies that enhance its ingestion and lysis by phagocytic cells. 3. Neutralization: IgG inactivates viruses by binding to their surface and neutralize toxins by blocking their active sites. 4. Antibody-dependent cell-mediated cytotoxicity: Used to destroy large organisms (e.g.: worms). Target organism is coated with antibodies and bombarded with chemicals from nonspecific immune cells. 5.Complement Activation: Both IgG and IgM trigger the complement system which results in cell lysis and inflammation. Erythroblastes acidophiles Description • Hématies nucléées Observation • • • • • • Moelle stimulée ou irritée Hyperrégénération de la lignée rouge après hémorragie ou hémolyse Dysérythropoièse Infiltration maligne Myélofibrose Post splénectomie Précipités d’Hémoglobine H Description • Granules très nombreux de petite taille visibles au au bleu de crésyl Observation • • • Hémoglobinose H Syndrome myéloprolifératifs dysérythopoièse Corps de Heinz Description • Observation • • • Corpuscules de 0,3µm de diamètre visibles après coloration spéciale par l e bleu de crésyl brillant correspondant à l’hémoglobine dénaturée Hémolyse toxique Hémolyse par des agents oxydants chez les sujets déficients en glutathion ou ayant une Hémoglobine instable • ß Tthalassémie • Post splénectomie MGG d’après atlas hématologie F.G.H Hayhoe editions Flammarion 1970 Parasites Plasmodium falciparum Plasmodium vivax • Lames du service d’hématologie de l’hôpital de Saint Denis (93) 2002 Plasmodium falciparum Photos Microscopie Electronique D’après l’ouvrage « les Cellules du Sang » M.BESSIS Editions Masson 1972 avec leur autorisation Microscopie optique Viviane GUILLAUME Lames provenant pour la plupart du service d’ hématologie CHU La Pitié Salpêtrière pendant la préparation du DERBH et du CHU de Nancy avec l’aimable autorisation de Mr le DrVISANICA