What's antibody chain?

Sorry, this is a literary site and I wouldn't be able to give you a good answer. I'm sure you can find it on-line though.

Antibody is protein with distinctive structure, making up of four polypeptide chains, which are held together by disulphide bridges. Each antibody has two long, or heavy, chains and two short, or light, chains. The light chain is at the end of one of the heavy chains. The four chains are held together in a shape of Y, which allows flexibility so antibodies can bind together.

As far as I am concerned, antibody chain is the binding material.

The specificity of the antibody is determined by the antigen antibody complex.

Please visit https://www.creative-biolabs.com/preciab/antibody-antigen-complex-analysis.htm to refer detailed information