Antibodies – Production, Structure, Domains, Types (IgG, IgD, IgA, IgE, IgM)

This video is part 2 of Acquired immunity – Antibodies

Components of an Antibody: 5:31
Domains: 7:32
IgG: 8:37
IgM: 9:50
IgA: 11:53
IgD: 13:39
IgE: 14:22
Differences between antibodies: 15:17
Table to memorize: 15:56
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
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:
Light Chain
Heavy Chain
Variable Part

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


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