Each antibody (immunoglobulin) used to defend against infection and other aggressions consists of a pair of heavy chains (G, A, M) and a pair of light chains (kappa or lambda). Normally, plasmocytes (white cells) make complete antibodies with the kappa and lambda chains in roughly equal amounts (kappa/lambda ratio between 0.26 and 1.65). Measurements of free kappa and lambda chains and their ratio are usually made following the discovery of an anomaly in protein electrophoresis and immunofixation. In some cases, even in the absence of an electrophoresis anomaly, there may be abnormal production of free chains.
Abnormal levels of kappa or lambda chains shall be interpreted by taking into account clinical data and the ka/la index. When the index is normal, the increase or decrease of one of the free chain fractions is accompanied by a change in the same direction of the other fraction. High production of kappa and lambda chains may be due to a normal immune response (polyclonal elevation with normal ka/la index). Low levels of kappa and lambda fractions with a normal index can be caused by any condition that interferes with the production of bone marrow cells. See also the interpretation of the free ka/la index.