Immunoglobulin light chain

The **immunoglobulin light chain** is a small polypeptide subunit that forms part of an antibody molecule. Each antibody consists of two identical heavy chains and two identical light chains, which together create the characteristic Y-shaped structure. The primary function of the immunoglobulin light chain is to contribute—along with the heavy chain—to forming the antigen-binding site at each arm tip through its variable region. There are two types in humans: kappa (κ) and lambda (λ), encoded by separate gene loci. Each B lymphocyte produces only one class—either κ or λ—for its lifetime. Light chains play a critical role in immune defense by enabling antibodies to specifically recognize diverse antigens. In healthy individuals, there is a typical serum ratio between kappa and lambda types; significant deviations may indicate clonal expansion seen in malignancies like multiple myeloma or lymphoma. Free circulating immunoglobulin light chains can be measured as biomarkers for these conditions. Pathologically increased levels may result from neoplastic plasma cells producing excess monoclonal free light chains, leading to their deposition in tissues—a hallmark feature of AL amyloidosis—or excretion into urine as "Bence Jones proteins." Elevated polyclonal free IgLCs also occur during inflammation but without clonal dominance. Immunoglobulin molecules—including their constituent heavy and **light** chains—are not direct drug targets but serve as important diagnostic markers for several hematologic diseases.

Other names

Ig light chainAntibody light chainLight chain (of immunoglobulin)IGK (for kappa type)IGL (for lambda type)