Immunoglobulin lambda free light chain (Igλ FLC)

Immunoglobulin lambda free light chains (Igλ FLCs) are low molecular weight proteins produced by plasma cells as byproducts of antibody synthesis (NIH, 2013). Under physiological conditions, these proteins are produced in slight excess of heavy chains and are rapidly cleared from the circulation by the kidneys (MedlinePlus, 2024). However, in plasma cell dyscrasias such as AL amyloidosis, monoclonal lambda light chains are overproduced and undergo misfolding into toxic soluble aggregates and insoluble amyloid fibrils (NIH, 2024). These fibrils deposit in vital organs, most notably the heart and kidneys, causing progressive tissue damage and organ failure (AstraZeneca, 2025). While traditional therapies focus on eliminating the underlying plasma cell clone, novel therapeutic agents like birtamimab and anselamimab are designed to directly target and clear these misfolded light chain deposits (Prothena, 2024; Alexion, 2026). Monitoring the levels and ratio of free light chains in the serum is essential for the diagnosis, risk stratification, and treatment monitoring of patients with these disorders (NIH, 2023).

Other names

Lambda free light chainλ-FLCImmunoglobulin light chain lambdaFree lambda light chainBence-Jones protein

Neutralization of toxic soluble light chain aggregates and promotion of macrophage-mediated phagocytic clearance of insoluble amyloid deposits.