Immunoglobulin light chains that are circulating in serum in a free state are called free light chains or Serum Free Light Chain. There are two types of immunoglobulin light chain produced in humans, designated by the Greek letters kappa (κ) and lambda (λ). This test looks for signs of antibodies called immunoglobulins in the patient's blood. When the patient has more light chains than heavy chains, those extra light chains are called 'free'. The more free light chains in the patient's blood, the more plasma cells the patient has which may mean there is a problem with the plasma cells.