Immunoglobulin heavy chain

Large polypeptide subunit of an antibody

disulfide bonds to two Ig light chains (green). The constant (C) and variable (V) domains are shown.

The immunoglobulin heavy chain (IgH) is the large polypeptide subunit of an antibody (immunoglobulin). In human genome, the IgH gene loci are on chromosome 14.

A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two

The heavy chain doesn't always have to bind to a light chain. Pre-B lymphocytes can synthesize heavy chain in the absence of light chain, which then can allow the heavy chain to bind to a heavy-chain binding protein.[3]

In mammals

Classes

There are five types of mammalian immunoglobulin heavy chain: γ, δ, α, μ and ε.

• Heavy chains α and γ have approximately 450 amino acids.
• Heavy chains μ and ε have approximately 550 amino acids.^[4]

Regions

Each heavy chain has two regions:

• a constant region (which is the same for all immunoglobulins of the same class but differs between classes).
  • Heavy chains γ, α and δ have a constant region composed of three tandem (in a line next to each other) immunoglobulin domains but also have a hinge region for added flexibility.^[5]
  • Heavy chains μ and ε have a constant region composed of four domains.^[4]
• a variable region that differs between different
  clone. The variable domain of any heavy chain is composed of a single immunoglobulin domain. These domains are about 110 amino acids long.^[6]