Free Light Chains of Immunoglobulins in Serum from Patients with Rheumatoid Arthritis, Sarcoidosis, Chronic Infections and Pulmonary Cancer

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Abstract
Free L chains of Ig were measured in serum from 181 patients with rheumatoid arthritis (RA), sarcoidosis, pulmonary tuberculosis, pulmonary cancer and chronic bronchitis, i.e., patients with long-term stimulation of the immune system. Increased concentrations of L chains were found in patients with active sarcoidosis; the L chain level appeared to be a marker of disease activity in sarcoidosis. The mean (.+-. SD) concentration of .kappa. plus .lambda. chains in active sarcoidosis of more than 2 yr duration was 38.3 .+-. 13.7 mg/l, that is twice the concentration of 19.4 .+-. 5.5 mg/l found in normals. Some patients with seropositive RA also had increased serum values. The L chain concentrations in seropositive RA were correlated to the severity of the disease measured by clinical staging and laboratory tests. A modest increase in L chains was observed in 1 patient with tuberculosis, and in 2 patients each with chronic bronchitis and pulmonary cancer.