Serum free light chains in solid organ transplant recipients

Immunoglobulin is built by a pair of identical heavy and a pair of identical light chains. Light chains are produced in excess compared to heavy chains. Free light chains (FLCs) are those which are not combined with heavy chains. Currently, numerous assays are available for the measurement of serum FLCs (sFLCs). These assays cannot be used interchangeably, and renal function should be taken into account in interpreting test results. Levels of kappa and lambda sFLCs are usually used to diagnose and monitor plasma cell dyscrasias. However, the clinical relevance of sFLCs is being investigated in patients with a variety of diseases, including patients after transplantation. There are contradictory results regarding the usefulness of sFLCs in the prediction of post-transplant lymphoproliferative disorder (PTLD). However, it seems that sFLCs may be helpful in the prediction of early-onset PTLD. Some studies have shown that low levels of sFLCs are associated with a higher risk of infection in patients after transplantation. This review summarizes and highlights recent advances in the utility of sFLCs in the prediction of PTLD and infection, and inflammation assessment in patients after solid organ transplantation. Moreover, the influence of immunosuppressive treatment on sFLCs levels is described briefly.