B cell receptor

The BCR contains 2 heavy chains and 2 light chains (κ or λ) held together by disulfide bonds. Each chain has a variable region and a constant region.

An H chain contains 4-5 Ig domains. An L chain contains 2 Ig domains.

A single BCR has 2 antigen-binding sites. Each antigen-binding site has 3 hypervariable regions.

BCRs recognize unprocessed, 3-D antigens that can be in the form of carbohydrate, lipid or protein.