Patients with some inflammatory diseases have been shown to have increased levels of immunoglobulin light chains. In this study, we measured the concentrations of immunoglobulin kappa and lambda light chains in sera of patients with juvenile idiopathic arthritis (JIA) (study group), familial mediterranean fever (FMF) (disease control group) and in healthy children. Our aim was to compare immunoglobulin light chain levels with other well-known markers of inflammation, such as the erythrocyte sedimentation rate (ESR) and the acute phase reactants (APRs), serum amyloid A (SAA) and C-reactive protein (CRP), to find out if immunoglobulin light chain determinations have any discriminating value in the follow-up of these patients.
ESR, CRP, SAA, kappa and lambda chain levels and lambda/IgG ratio showed a statistically significant difference between active and remission stages in JIA patients. Kappa correlated very well with SAA and ESR in both stages. On the other hand, lambda correlated with SAA and ESR only in the remission period. There was no significant difference in kappa and lambda chain levels between active and remission stages in FMF patients. In addition, kappa and lambda chain concentrations showed no correlation with other markers of inflammation and immunoglobulin levels neither in entire FMF group nor in different subgroups with respect to clinical status. Immunoglobulin light chains kappa and lambda as well as levels of three markers of inflammation were found to be significantly higher in JIA patients who were in the active stage of disease when compared to data of healthy children
Ig light chains especially kappa chain concentrations are helpful to determine disease stage in JIA patients but with our current data, they do not exhibit superiority to any of the classical tests for inflammation.