Each heavy chain has two regions, the constant region and the variable region.

The scFv is then constructed from the antibody's variable regions.

The variable region determines what antigen the T cell can respond to.

The protein shows sequence similarity to the variable regions of some immunoglobulin supergene family member proteins.

The V-shaped top portion of the antibody molecule, called the variable region, is the target-seeking part.

Antibodies have a 'variable region' in their structure.

The variable regions are often constructed with the help of fragment libraries.

These contain segments of the variable regions of both the light and heavy chains, held together by a peptide created through genetic engineering.

Since the variable region does not change, class switching does not affect antigen specificity.

During class switching, the constant region of the immunoglobulin heavy chain changes but the variable regions, and therefore antigenic specificity, stay the same.