adaptive immune response
DESCRIPTION
ADAPTIVE IMMUNE RESPONSE. When the body is exposed to an antigen Innate Immunity Adaptive Immunity (Acquired). Active immunity • B cells encounter antigens and produce antibodies • Active immunity can be naturally or artificially acquired Passive Immunity - PowerPoint PPT PresentationTRANSCRIPT
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ADAPTIVEIMMUNE RESPONSE
When the body isexposed to an antigen
Innate Immunity
Adaptive Immunity(Acquired)
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Active immunity•B cells encounter antigens and produce antibodies• Active immunity can be naturally or artificially acquired
Passive Immunity• Antibodies are obtained from someone else
• Conferred naturally from a mother to her fetus• Conferred artificially from immune serum or
gamma globulin• Immunological memory does not occur
• Protection provided by “borrowed antibodies”
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Types of Adaptive Immune Response1 .Cell-mediated immune
response (CMIR) – T cells2. Humoral immune response – B cells
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Humoral Immune ResponseB lymphocytes with specific receptors bind to aspecific antigen The binding event activates the lymphocyte toundergo clonal selection A large number of clones are produced (primaryhumoral response) Most B cells become plasma cells
Produce antibodies to destroy antigens Activity lasts for four or five days
Some B cells become long-lived memory cells(secondary humoral response)
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Activation of B cellsRecognition of antigen by B cells• B cells recognize their cognate antigen in its native form.• They recognize free antigens in the blood or lymph using their B-
cell receptor (BCR) or membrane bound-immunoglobulin• After antigen recognition, the B cell ingests the whole protein
antigen and processes it into peptides for presentation to activated T cells.
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Antibodies 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.
Valence of an antibody: Number of antigen binding sites. Most are bivalent.
Belong to a group of serum proteins called immunoglobulins (Igs).
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Antibody Structure Monomer: A flexible Y-shaped molecule with four
polypeptide chains:– 2 identical light chains
– 2 identical heavy chains 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: Important because they can bind to complement
or cells.
held together by disulphide bridges
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Antibody Structure
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Hinge Region
The region at which the arms of the antibody molecule forms a Y is called the hinge region because there is some flexibility in the molecule at this point.
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An antibody digested by papain yields three fragments: two Fab fragments and one Fc fragment
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General Functions of ImmunoglobulinsA. Antigen binding (primary function)• Immunoglobulins bind specifically to one or more
antigenic determinant and can result in protection of the host.
Valency: Is the number of antigenic determinants that an
individual antibody molecule can bind. The valency of all antibodies is at least two and in some instances more.
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B. Effector functions Fixation of complement lysis of cells, release of
biologically active molecules
Binding to various cells: phagocytic cells, lymphocytes, mast cells, and
basophils have receptors that bind immunoglobulins and thus get activated.
Some immunoglobulins also bind to receptors on placental trophoblasts, leading to transfer of the Igs across the placenta (provide immunity to the fetus)
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Immunoglobulin Classes• IgG - Gamma (γ) heavy chains• IgM - Mu (µ) heavy chains• IgA - Alpha (α) heavy chains• IgD - Delta (δ) heavy chains• IgE - Epsilon (ε) heavy chainsImmunoglobulin Subclasses• IgG Subclasses
– IgG1 - Gamma 1 (γ1) heavy chains– IgG2 - Gamma 2 (γ2) heavy chains– IgG3 - Gamma 3 (γ3) heavy chains– IgG4 - Gamma 4 (γ4) heavy chains
• IgA subclasses– IgA1 - Alpha 1 (α1) heavy chains– IgA2 - Alpha 2 (α2) heavy chains
ImmunoglobulinLight Chain Types:Kappa )κ( Lambda )λ(
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Different Immunoglobulins
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TypeNumber of Ag binding sites
Site of actionFunctions
IgG2•Blood
•Tissue fluid
•Can cross placenta
•Increase macrophage activity
•Antitoxins
•Agglutination
IgM10•Blood
•Tissue fluid
Agglutination
IgA2 or 4•Secretions )saliva, tears, small intestine, vaginal, prostate, nasal, breast milk(
•Stop bacteria adhering to host cells
•Prevents bacteria forming colonies on mucous membranes
IgE2Tissues•Activate mast cells
HISTAMINE
•Worm response
IgD2B-cell surfaces where it functions as a receptor for Ag.
•B cell activation
Cε4