Antibodies (Origin, Components, Domains, IgG, IgM, IgA, IgD, IgE) +TABLE - Immunology
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This video is part 2 of Acquired immunity - Antibodies
Content
0:00 Introduction
0:06 Where do Antibodies Come From?
5:31 Components of an Antibody
7:32 Domains
8:37 IgG
9:50 IgM
11:53 IgA
13:39 IgD
14:22 IgE
15:17 Differences Between Antibodies
15:56 Table to Memorize
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All information in my immunology videos are from:
Book: Immunology, Eighth Edition by David Male, Jonathan Brostoff, David Roth and Ivan Roitt
Additional research in PubMed
University lecture materials
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Antibodies: Plasma proteins
Where they come from:
1. B-cell (with BCR - IgG/D) bind to antigen
2. Present it on MHC II
3. APC activates a naive Th cell through TCR (CD4 and CD3), B7/CD28 and IL-4 receptor
4. Naive T helper cell secretes IL2 (autocrine)
5. Becomes an active Th2
6. Th2 helps active B-cell through CD40L/CD40 and T cell receptor.
7. IL-4, IL-5, IL-8, IL-10, IL-2, IFN gamma released depending on what type of antibody is needed.
Components of an Antibody:
Has:
Light Chain
Heavy Chain
Variable Part
Constant
Becomes:
VL, Vh, CL, Ch1, Ch2, Ch3
CL-Ch1 Connected through disulfide bonds
two parts of antibody connected through a Hinge which give the antibody motility
divided into Fab (fragment antigen binding) and Fc (Fragment crystalizable region)
Antibody Domains:
Variable region - Antigen binding sites
Ch1 region - Determine Allotype
Ch2 region - Binds Complement
Ch3 region - Binds Cells
Variants of chains:
Light Chain:
Lambda Chain
Kappa Chain
Heavy Chain:
Gamma Chain (IgG)
My Chain (IgM)
Alpha Chain (IgA)
Delta Chain (IgD)
Epsilon Chain (IgE)
Functions of IgG:
Exists as: Monomeric (plus subtypes)
Amount in Plasma: 75%
IgG is only antibody that pass through placenta. so we get igG from mothers.
Direct Opsonization
Activate Complement System
IgG responsible for the secondary response in humoral immune response because memory B-cells are made to produce IgG
Functions of IgM:
Pentameric (with a J-Chain) and Monomeric on B-cells
''Youngest Class'' since a fetus can produce them.
IgM reacts as the primary response, but no memory as they are produced by T-cell independent B cell proliferation
Complement activation
Functions of IgA:
Dimeric (J-chain), Monomeric and Trimeric
Found at mucosal entry
Alpha plasma cells secretes IgA. IgA binds to epithelium through poly IgA receptors and transported through cytoplasm through endocytosis and sent out through proteolytic cleavage
Many microorganisms can cleave IgA
Functions of IgD:
Under 1% in blood
Localized on surface of B-cells
Monomeric
Functions of IgE:
Very low amount in blood
Monomeric
Mast Cell
Responsible for Type 1 hypersensitivity. Made after sensitization.
Increase amount of IgE during allergic diseases and parasite infections.
Differences between Immunoglobulins:
Idiotypic differences: Differ in variable region
Isotypic Differences: Antibodies differ in constant region
Allotypic Differences: Difference between alleles of same constant gene