Intrathecal synthesis of free immunoglobulin light chains and IgM in initial multiple sclerosis.

We studied the intrathecal synthesis of free kappa, free lambda immunoglobulin light chains and of IgM in 33 consecutive patients with possible or probable MS at the time of their first diagnosis. Nineteen patients presented free kappa or lambda light chain bands in CSF after agarose isoelectric focusing, protein transfer to nitrocellulose and immunostaining with specific antisera. Nineteen patients had increased CSF levels of free kappa light chains as measured with a competitive ELISA. Fourteen had an increased IgM index, as evaluated with a sandwich ELISA. Twenty-six patients displayed CSF oligoclonal IgG bands in CSF and 25 had cerebral magnetic resonance imaging lesions suggestive of MS. The local production of free immunoglobulin light chains and IgM is often detected in the CSF of patients with early MS.