Polyclonal Immunoglobulin Free Light Chains as a PotentialBiomarker of Immune Stimulation and Inflammation

C-reactive protein (CRP)3 is an established biomarker of acute and chronic inflammation. The hepatic synthesis of CRP is closely regulated by inflammatory cytokines, in particular interleukin-6. The CRP concentration increases rapidly in response to an inflammatory event, peaks within 48 hours, and often increases 100-fold. Bacterial infections and large burns are associated with the largest increases in serum CRP, and serial measurements of CRP in patients with these conditions can allow assessment of disease progression or the response to treatment. More recently, the commercial introduction of nephelometric assays has allowed the detection of small changes in CRP, even within the reference interval, and such increases have been associated with cardiovascular disease (1) and cancer (2).The assessment of inflammation by CRP measurement provides clinicians with a valuable tool to use across a number of clinical settings; however, CRP reflects only the activity of innate immunity. If the activity of both the adaptive and innate immune systems could be determined simultaneously, it is possible that additional diagnostic, prognostic, or monitoring information could be gained. The adaptive immune system consists of several specialized cell types and processes that allow protection from challenges by pathogens and the ability to recognize and remember each individual antigen. The individual identification of each antigen and the ability to mount a larger, more rapid response to the antigen on repeat exposure are essential to the success of this system of immunologic memory. A key component of this process is the production of antibodies by plasma cells of the B-cell lineage. Antibodies or immunoglobulins are proteins that consist of 2 identical heavy chains (HCs) and 2 identical light chains (LCs). Antibodies are typed by their HCs into 5 categories (IgA, IgD, IgE, IgG, and IgM), each of which has 2 isotypes, κ or λ LC. During …