Light chain

Overview
A light chain is the small polypeptide subunit of an antibody (or immunoglobulin); a typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains.

In humans
There are two types of light chain in mammals,
 * lambda (λ) chain (1, 2, 3, and 4)
 * kappa (κ) chain (only one type)

In other animals
Other types of light chains can be found in lower vertebrates, such as the Ig-Light-Iota chain of Chondrichthyes and Teleostei.

Camelids are unique among mammals as they have fully functional antibodies which have two heavy chains, but lack the light chains usually paired with each heavy chain. The functional role of this separate repertoire is unknown as yet.

Structure
Only one type of light chain is present in a typical antibody, thus the two light chains of an individual antibody are identical.

Each light chain is composed of two tandem immunoglobulin domains:
 * one constant (IgC) domain
 * one variable domain (IgV) that is important for binding antigen

The approximate length of a light chain protein is from 211 to 217 amino acids.