Background Plasma and B cells have been implicated in multiple sclerosis (MS). The presence of intrathecal oligoclonal IgG and free light chains (FLCs) is a feature of MS and rituximab has been shown to be effective in MS. Plasma and B cells produce excess FLC that are excreted in the urine. Urinary FLC excretion is therefore a putative marker of MS activity.
Objectives To confirm that subjects with demyelinating diseases have increased urinary excretion of FLCs. Methods in a cross-sectional study, urine FLCs were measured by ELISA and presented as a ratio to albumin to control for urine concentration. 40 patients with MS and 10 patients with clinically isolated syndromes (CIS) were compared to 20 subjects with posterior uveitis (PU), 19 with AIDS, 34 with rheumatoid arthritis (RA) and 19 normal controls (NC).
Results Subjects with DD, PU, RA and AIDS have significantly higher free kappa, lambda and total urinary light chain excretion than NC (p<0.01). Subjects with established MS and CIS had higher excretion of free kappa, lambda and total urinary light chain excretion than NC (p=0.05). Urinary FLC excretion did not correlate with gadolinium-enhancing lesions on MRI.
Conclusions Increased urinary FLC are a biomarker of plasma cell and B cell activity and raised in subjects with MS and CIS. Further studies are required to see if raised urine FLC excretion correlates with MS disease activity and whether it is predictive of the development of MS in subjects with CIS.