11. Antibodies - Notes taken from the lecture of Sir Joseph Joy Banzon, RMT PDF

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IMMUNOLOGY SEROLOGY ANTIBODIES ANTIBODIES glycoprotein substances synthesized plasma cells in response to antigenic stimulation antigenic specificity is known IMMUNOGLOBULINS considered to be the humoral branch of the immune response part of the fraction of serum protein (when subjected to electroph...

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IMMUNOLOGY & SEROLOGY

ANTIBODIES ANTIBODIES - glycoprotein substances synthesized by plasma cells in response to antigenic stimulation - antigenic specificity is known IMMUNOGLOBULINS - considered to be the humoral branch of the immune response - part of the γ-globulin fraction of serum protein (when subjected to electrophoresis, they will appear on γ-band) - antigenic specificity is not known PROPERTIES OF AN ANTIBODY:  Protein in nature (82-96% Polypeptide; 2-14% Carbohydrate)  has high molecular weight  Present in all body fluids CLASSIFICATIONS OF ANTIBODIES: I. According to its Sedimentation Constant: IMMUNOGLOBULIN SEDIMENTATION (Ig) COEFFICIENT IgM 19s IgE 8s IgD 7s Secretory IgA 9s; 11s; 13s Serum IgA 7s IgG 7s

MOLECULAR WEIGHT (Daltons) 900,000 D 190,000 D 180,000 D 170,000 D 160,000 D 150,000 D

II. According to temperature at which they react: 1. COLD ANTIBODIES (IgM) - reacts @ 4°c - RT - Example: ABO antibodies 2. WARM ANTIBODIES (IgG) - reacts @ 30°c - 37°c - Example: Rh antibody III. According to occurrence: 1. NATURAL ANTIBODIES - produced even without antigenic stimulation - Example: ABO antibodies 2. IMMUNE / ACQUIRED ANTIBODIES - produced only when there’s antigenic stimulation - Example: Rh antibodies IV. According to the species which produce them: 1. ISOANTIBODIES / ALLOANTIBODIES - Ab from other individual of the same species 2. HETEROPHILE ANTIBODIES - Ab from other species

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

ANTIBODIES V. According to its reaction with an antigen: 1. AGGLUTININS - Ab which reacts with Agglutinogen - involved in Agglutination reaction - Nature: Particulate/Cellular Antigen 2. PRECIPITINS - Ab which reacts with Precipitinogen - involved in Precipitation reaction - Nature: Soluble Antigen 3. AGGLUTINOIDS - Ab which reacts with Agglutinins modified by heat - it can still react with an Ag but the reaction is not visible 4. HEMAGGLUTININS - Ab which causes RBC clumping - involved in Hemagllutination reaction 5. LYSINS - Ab which causes lysis provided that there’s a Complement Activation - Examples: Bacteriolysin / Leukocidin (Panton Valentine Factor) 6. OPSONINS - Ab that coats Ag to be ready for Phagocytosis - Example: Ig 7. NEUTRALIZING ANTIBODIES - Ab that render organisms to be harmless 8. ALLERGIC ANTIBODIES - Ab that reacts with Allergen 9. ANTITOXINS - Ab that inhibits harmful effects of toxin 10. COMPLEMENT FIXING ANTIBODIES - Ab that activates the Complement 11. BLOCKING / INHIBITORY ANTIBODIES - Ab that blocks certain reaction VI. According to their in-vitro behavior: COMPLETE Ab INCOMPLETE Ab Example IgM IgG Univalent, blocking, coagglutinating, Synonyms Bivalent, Saline-acting conglutinating Reaction Saline acting Albumin acting Late in Occurrence Early in immunization immunization Response to Thermolabile Thermostable temperature Ability to cross can’t cross in the can cross the Placenta placenta Placenta

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

ANTIBODIES STRUCTURE OF AN IMMUNOGLOBULIN: 1. HEAVY CHAIN - dictates the class of Ig - two heavy chains in an Ab should be identical - produced in Chromosome #14 - has five principal antigenic types: a. Gamma = IgG b. Alpha = IgA c. Mu = IgM d. Delta = IgD e. Epsilon = IgE 2. LIGHT CHAIN - has two antigenically defined types: a. Kappa = found in Chromosome #2 b. Lambda = found in Chromosome #22 3. DISULFIDE BONDS - chemical bonds essential for the normal 3 dimentional structure of Ig - has two kinds: a. INTERCHAIN = connects heavy chain to light chain or vice versa b. INTRACHAIN = connects the domains of heavy chain & light chain 4. HINGE REGION - the flexible part of an antibody located in the heavy chain - it is more exposed to enzymes & chemicals (papain acts here to produce Fab & Fc fragments) - rich in PROLINE which is needed for the flexibility of the hinge - all Ig have Hinge region except IgM & IgE (they are flexible based on the pairing of Ch2 Domains in such way to confer flexibility to Fab arms) 5. DOMAINS - are globular gerions on polypeptide chain stabilized by intrachain disulfide bonds a. Domains on the light chain:  VL  CL b. Domains on the heavy chain:  VL + VH = antigen binding sites  CH1 = binds to C4b  CH2 = binds to C1q if Ab is IgG  CH3 = binds to C1q if Ab is IgM; also binds to T-cell, B-cell, Platelets, Mast cell, Macrophages, & Monocytes  CH4 = only present in IgM & IgE  CH2 + CH3 = binds to Staphylococcal Protein A, Placental Syncytiotrophoblast; also binds in NK cells & Neutrophils VARIABLE REGION Amino acid sequence subject to change Amino terminals (NH2) concerned with binding to Ag

CONSTANT REGION Amino acid sequence is fixed Carboxyl terminal (COOH) concerned with binding to host tissue

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

ANTIBODIES 6. FRAGMENTS - has two kinds: a. FRAGMENT ANTIGEN BINDING (FAB) - also called as the variable region - each fragment contains 1 antigen binding site - has 1 Light chain & ½ of Heavy chain b. FRAGMENT CRYSTALLIZABLE (FC) - also called as the constant region - crystallizes @ 4°c - binds to the host tissues - has ½ of Heavy chain MONOMER - basic structural unit of an antibody - has two antigen binding site - Example: IgD, IgE, IgG, IgA POLYMER - Ig composed of more than a single basic monomeric unit - Examples: a. DIMER - has four antigen binding site - Example: Secretory IgA b. PENTAMER - has ten antigen binding site - Example: IgM J-CHAIN - polypeptide chain which normally holds polymeric Ig SECRETORY COMPONENT - a substance attached to Polymeric Ig found on secretions ENZYME DIGESTION: 1. Cleavage with PAPAIN ENZYME - cleaves before the hinge region - Products: 2 FAB, 1 FC 2. Cleavage with PEPSIN ENZYME - cleaves after the hinge region - Products: F(AB)2 & 1 FC 3. Reduction using MERCAPTOETHYLAMINE— destroys disulfide bonds 4. Pepsin digestion + reduction 5. Papain digestion + reduction

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA

IMMUNOLOGY & SEROLOGY

ANTIBODIES GENETICS OF IMMUNOGLOBULINS: - needed in the synthesis of fragments & parts of Ab molecule 1. VARIABLE (V) gene 2. DIVERSITY (D) gene 3. JOINING (J) gene 4. CONSTANT (C) gene IMMUNOGLOBULIN VARIABLITY: 5. ISOTYPIC VARIABILITY = variation in the heavy chain which determines Ig class 6. ALLOTYPIC VARIABILITY = variation in the constant region which determines Ig subclass 7. IDIOTYPIC VARIABILTIY = variation in the variable region which gives the antibody its specificity THEORIES OF ANTIBODY PRODUCTION: 1. EHRLICH’S SIDE CHAIN THEORY - by: PAUL ERHLICH - Certain cells has had specific surface receptors for antigen that were present before contact with antigen occurred. Once antigen was introduced, it would select the cell with proper receptors, combination would take place and then receptors will break off and enter the circulation as antibody molecules. New receptors will be formed in place of those broken off and this process could be repeated 2. THE TEMPLATE THEORY - by: FELIX HAUROWITZ - Antibody-producing cells are capable of synthesizing a generalized type of antibody, and when contact with an antigen occurs, the antigen serves as a mold or template and alters protein synthesis so that antibody with a specific fit is made. The “molded” antibody then enters the circulation, while the antigen remains behind to direct further synthesis 3. SELECTIVE THEORY - Assumes that antibodies are synthesized in a manner similar to that of other proteins. Instructions for their synthesis are provided by genetic elements in the nucleus of the cell rather from the antigen 4. CLONAL SELECTION THEORY - by: NIEL JERNE & MACFARLANE BURNET - Individual lymphocytes are genetically pre-programmed to produce one type of immunoglobulin, and that specific antigen finds or selects those particular cells capable of responding to it, causing these to proliferate. Repeated contact with the antigen would continually increase a lymphocyte pool

JOYCE ANN S. MAGSAKAY

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BS MEDICAL LABORATORY SCIENCE

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OLFU VALENZUELA...