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

Summary 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%. A new procedure based on a semiquantitative Western blot analysis was developed to study saliva immunoglobulin free light chain (FLC) monomers (25 kDa) and dimers (50kDa) of κ and λ type. Striking differences were revealed by comparing saliva FLC monomer‐dimer patterns of active MS patients (a2, b2, c2, d2, e2) versus patients in remission (c1, d1, e1) or healthy subjects (a1 and b1): active MS patients showed abnormally elevated level of FLC monomers and/or of both monomeric and dimeric FLC. The developed technique may serve as a new non‐invasive complimentary tool to evaluate the MS disease state by differentiating active MS from remission with sensitivity of 89% and specificity of 80%.