Monoclonal immunoglobulin light chain in urine of patients with B lymphocytic disease: its source and use as a diagnostic aid.

The presence of tumour-related monoclonal light chain has been sought in urine as an immunochemical aid in the diagnosis of B lymphocytic neoplasms. The technique of isoelectric focusing in agarose followed by immunofixation has been applied to concentrated urines from 41 patients. In chronic lymphocytic leukaemia involving neoplastic B lymphocytes, monoclonal light chain was detected in 14 out of 19 patients investigated. For 2 of the positive cases (one kappa light chain type and one lambda light chain type) the urinary light chains were compared directly with culture fluids obtained after incubation of the corresponding neoplastic cells obtained from the patient's peripheral blood: identity of the light chains from urine and cells was established by isoelectric focusing demonstrating for both patients that the tumour cells were the source of the urinary light chain. In patients with non-Hodgkin's lymphoma involving neoplastic B lymphocytes, urinary monoclonal light chains were found in 7/16 of those studied. Such light chains were not detected in 11 control subjects, in 3 patients with true histiocytic tumours or in 2 patients with enlarged reactive lymph nodes. The technique is simple to perform and provides information for diagnosis and possibly monitoring of B cell neoplasms.