Which of the following statements about immunoglobulin light chains is true?

• A. Each immunoglobulin monomer has either one kappa or one lambda chain.
• B. There are two types: kappa and lambda.
• C. They consist of constant regions only.
• D. They form part of the Fc fragment.

Answer: (B)

Light chains in immunoglobulins come in two types: kappa and lambda. An antibody molecule has two light chains, and both are the same type—either two kappa or two lambda chains—paired with two heavy chains. This is what makes the two-type arrangement the true statement. Light chains are not just constant regions; they contain a variable region that participates in antigen binding and a constant region, and they are part of the Fab fragment, not the Fc. The Fc fragment is formed by the constant regions of the heavy chains.