SFLC

SFLC in the glossary for Waldenström's macroglobulinemia

SFLC (serum-free light chain) – Proteins produced by plasma cells, which link together with other proteins (heavy chains) to form immunoglobulins (antibodies) that target and neutralize specific infectious agents such as bacteria and viruses

Free light chains (FLC) or serum free light chains (SFLC) refer to those that are not part of whole (intact) immunoglobulins and are present in the blood. Serum concentrations of FLCs are dependent on the balance between production and renal clearance. Serum FLCs (sFLCs) are rapidly cleared through the renal glomeruli with half-lives of between 2 and 6 hours before being metabolised. Under normal circumstances, little protein escapes to the urine so sFLC concentrations are a more accurate representation of production levels. When there is increased polyclonal immunoglobulin production and/or renal impairment, both κ and λ sFLC concentrations can increase 30- to 40-fold. However, the relative concentrations of κ to λ (i.e., the κ/λ ratio) remain unchanged, or only slightly increase. In contrast, the production of a monoclonal excess of one FLC type in patients with a plasma cell dyscrasia gives an abnormal serum κ/λ ratio, providing a numerical indicator of clonality.¹