Glossary
FREE LIGHT CHAINS (FLCs)
During immunoglobulin synthesis, plasma cells produce slightly more light chains compared to heavy chains. The proteins that remain unused in assembling an entire immunoglobulin, are called free light chains (FLC). FLC half-life is 2-4 hours for the kappa chains and 3-6 hours for lambda chains that are present in the serum as dimers, as their reduced size allows them to be easily filtered by the glomerulus. The difference in speed of renal filtration implies that the concentration of lambda chains in the serum can be greater, even if the synthesis favors kappa chains. Increased plasmat concentration may be due to a variety of clinical situations such as immune depression or stimulation, kidney failure or plasma cell dyscrasias. With the exception of the latter condition, however, kappa and lambda chain ratios remain normal. The presence of lymphoproliferative disorders can cause an unbalanced ratio between the two light chains (kappa or lambda) to be observed. An immunometric assay for the measurement of light chains in the serum was introduced in the early 2000s; the test is capable of detecting the sole FLC by means of antibodies directed against the hidden epitopes within the whole immunoglobulin. This measurement is unable to distinguish between polyclonal and monoclonal FLC; nevertheless, as mentioned above, an alteration in the kappa/lambda ratio provides evidence of a monoclonal lymphoplasmacellular proliferation.
Reference interval (mg/L)
κ FLC 3.3 – 19.4
λFLC 5.7 – 26.3
κ/λFLC 0.3 –1.2 0.26 – 1.65
See also:
• Glossary