Abstract: Immunoglobulin kappa chain (Igκ) is a light chain of immunoglobulin. The immunoglobulin gene consists of three different loci, including κ chain, lambda (λ) chain and heavy chain. In normal, the light chain of immunoglobulin usually binds with heavy chain to form functional immunoglobulin complex. Free κ or λ light chains (FLCs) can be produced in the process of immunoglobulin synthesis by B lymphocytes. It was thought that FLCs had no function, but now it has been reported that FLCs participate in several key processes of immune response. The concentration of FLCs is closely correlated with the prognosis of different diseases. FLCs can promote mast cell degranulation, resulting in the releasing of inflammatory mediators in inflammatory bowel disease. Furthermore, the high level of FLCs can be also detected in some autoimmune diseases. Besides the role of FLCs in non-tumor diseases, Igκ secreted by B lymphocytes in tumor stroma is related to tumor initiation and development. Here, we reviewed the structure and function of Igκ and its role in the pathogenesis of diseases.

Key words: immunoglobulin kappa-chains, B-lymphocytes, inflammation, neoplasms, kidney diseases, rheumatic diseases, heart failure