54. Antibodies - definition, structure, major class’s and functions. Flashcards Preview

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Flashcards in 54. Antibodies - definition, structure, major class’s and functions. Deck (14):
1

Antibodies are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies - triggered by antigens

Antibodies are glycoprotein molecules that are produced by plasma cells in response to an immunogen and which function as antibodies - triggered by antigens

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Structure: heavy + light chains. Disulfide bonds (either inter-chain or intra-chain). There are variable and constant regions, as well as the hinge region. Antibodies are made of oligosaccharides. Antibodies can occur in fragments resulting in a fab and Fc part. Fab part - antigen binding, Fc part - effector functions.

Structure: heavy + light chains. Disulfide bonds (either inter-chain or intra-chain). There are variable and constant regions, as well as the hinge region. Antibodies are made of oligosaccharides. Antibodies can occur in fragments resulting in a fab and Fc part. Fab part - antigen binding, Fc part - effector functions.

3

Antigen-antibody reactions follow the lock and key system. Basically this concept shows the antigen is the key and the antibody is the fitting lock. Antigen-antibody reaction is held by non-covalent bonds. Non-covalent bonds keep the antigen in the antibody combining sit. Electrostatic forces, Van der Waals forces are typically the types of bonds. These reactions are reversible due to non-covalent bonds.

Antigen-antibody reactions follow the lock and key system. Basically this concept shows the antigen is the key and the antibody is the fitting lock. Antigen-antibody reaction is held by non-covalent bonds. Non-covalent bonds keep the antigen in the antibody combining sit. Electrostatic forces, Van der Waals forces are typically the types of bonds. These reactions are reversible due to non-covalent bonds.

4

The strength of the antigen-antibody reaction is measured by affinity and avidity .

Affinity - the strength of a single antigenic determinant and a single combining site of the antibody. (sum of attractive + repulsive forces between the two)

Avidity - measure of overall strength of binding or an antigen. Influenced by valence of both antigen and antibody

The strength of the antigen-antibody reaction is measured by affinity and avidity .

Affinity - the strength of a single antigenic determinant and a single combining site of the antibody. (sum of attractive + repulsive forces between the two)

Avidity - measure of overall strength of binding or an antigen. Influenced by valence of both antigen and antibody

5

Antibodies have a certain specificity - the ability of a population of antibody molecules to react with only one antigen. Antibodies can distinguish the primary, secondary, tertiary structure of the antigen + the isomeric forms of the antigen.

Antibodies have a certain specificity - the ability of a population of antibody molecules to react with only one antigen. Antibodies can distinguish the primary, secondary, tertiary structure of the antigen + the isomeric forms of the antigen.

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Cross reactivity - the ability of a population of antibody molecules to react with more than one antigen. Cross reactivity occurs because the cross reacting antigen shares an epitope with the immunising antigen.

Cross reactivity - the ability of a population of antibody molecules to react with more than one antigen. Cross reactivity occurs because the cross reacting antigen shares an epitope with the immunising antigen.

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Structure continued: antibodies have different domains: the V1 + C1 domain and the Vh and Ch1-Ch3 (or Ch4) domain.

Structure continued: antibodies have different domains: the V1 + C1 domain and the Vh and Ch1-Ch3 (or Ch4) domain.

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Antibodies are classified as:

- IgG - gamma heavy chains

- IgG1 - gamma 1 heavy chains

- IgG2 - gamma 2 heavy chains

- IgG3…

Antibodies are classified as:

- IgG - gamma heavy chains

- IgG1 - gamma 1 heavy chains

- IgG2 - gamma 2 heavy chains

- IgG3…

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IgM - mu heavy chains

IgA - alpha heavy chains

IgD - delta heavy chains

IgE - epsilon heavy chains

IgM - mu heavy chains

IgA - alpha heavy chains

IgD - delta heavy chains

IgE - epsilon heavy chains

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IgA Found in mucosal areas - gut, respiratory tract, urogenital tract
Prevents colonisation by pathogens
Found in saliva, tears and breast milk

IgA Found in mucosal areas - gut, respiratory tract, urogenital tract
Prevents colonisation by pathogens
Found in saliva, tears and breast milk

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IgD Antigen receptor on B calls that havent been exposed to antigens
Activates basophils and mast cells to produce antimicrobial factors

IgD Antigen receptor on B calls that havent been exposed to antigens
Activates basophils and mast cells to produce antimicrobial factors

12

IgE Binds to allergens and triggers histamine release from mast cells and basophils
involved in allergy
protects against parasitic worms

IgE Binds to allergens and triggers histamine release from mast cells and basophils
involved in allergy
protects against parasitic worms

13

IgG Provides most of antibody-based immunity against invading pathogens.
the ONLY antibody that’s capable of crossing the placenta to give passive immunity to the
foetus

IgG Provides most of antibody-based immunity against invading pathogens.
the ONLY antibody that’s capable of crossing the placenta to give passive immunity to the
foetus

14

IgM Expressed on surface of B cells (monomer) and in a secreted form (pentamer) with a very high
avidity
eliminates pathogens in the early stages of B cell mediated (humoral) immunity before there’s
sufficient IgG

IgM Expressed on surface of B cells (monomer) and in a secreted form (pentamer) with a very high
avidity
eliminates pathogens in the early stages of B cell mediated (humoral) immunity before there’s
sufficient IgG

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