Immunoglobulin free light chains in saliva: a potential marker for disease activity in multiple sclerosis.

A new procedure was developed and applied to study immunoglobulin free light chains (FLC) in saliva of healthy subjects and patients with multiple sclerosis (MS). The procedure was based on a Western blot analysis for detection and semiquantitative evaluation of monomeric and dimeric FLCs. The FLC indices accounting for the total FLC levels and for the monomer/dimer ratios of κ and λ FLC were calculated, and the cut-off values of the FLC indices were determined to distinguish healthy state from MS disease. The obtained FLC index values were statistically different in the saliva of three groups: active MS patients, MS patients in remission and healthy subjects groups. Our FLC monomer-dimer analysis allowed differentiation between healthy state and active MS with specificity of 100% and a sensitivity of 88·5%. The developed technique may serve as a new non-invasive complementary tool to evaluate the disease state by differentiating active MS from remission with sensitivity of 89% and specificity of 80%.