Immunoglobulin lambda light chain constant region (None established; often referred to as "Ig lambda CL" or "Cλ" in scientific shorthand, but no universal abbreviation[3][4][6])

The **immunoglobulin lambda light chain constant region** is the portion of the antibody light chain that is invariant within the lambda subtype and is distinct from the variable region responsible for antigen binding[1][3][6][10]. In humans, immunoglobulin light chains exist as two types—kappa and lambda—each composed of a variable and a constant domain; every antibody molecule contains either two kappa or two lambda light chains, never a mix[1][6]. The constant region of the lambda light chain (Cλ) is encoded by several genes on chromosome 22 in a tandem array, with four active genes (lambda 1, 2, 3, 7) and three pseudogenes[6]. The Cλ region consists of approximately 105 amino acid residues and provides structural support, determining the light chain class but not participating in direct antigen binding[3][4][7][10]. Detection of increased levels of free lambda light chains or an altered kappa/lambda ratio in serum serves as an important biomarker for plasma cell neoplasms such as multiple myeloma, as well as for monitoring disease progression or response to therapy[1]. It is not a direct therapeutic target but is clinically significant as a diagnostic and prognostic marker.

Other names

Lambda light chain C regionC lambdaIg lambda constant regionIg CλImmunoglobulin lambda constant region

Not applicable as a drug target; aberrant lambda chain production may play a pathogenic role in diseases like amyloidosis, but no approved drugs target the constant region directly.