The role of free light chains in periodontitis and chronic inflammation

Background:
Periodontitis is a ubiquitous chronic inflammatory disease that destroys the supporting structures of teeth, ultimately leading to tooth loss. Periodontal disease is also associated with a range of systemic diseases including diabetes, cardiovascular disease, chronic kidney disease and rheumatoid arthritis. It is initiated by bacteria present in a biofilm at and below the gingival margin, however the subsequent tissue damage is the result of an exaggerated host inflammatory response within susceptible individuals.

Free light chains (FLCs) are circulating unbound immunoglobulin light chains released during plasma cell activation. Recent evidence suggests that increased FLC levels are biomarkers of systemic inflammation. Two types of FLCs are produced in humans, kappa (κ) and lambda (λ), which can directly activate leukocytes such as neutrophils, and increase their survival, leading to direct host tissue damage. Whilst neutrophils are the major type of white blood cell in the systemic circulation and in many host tissues including periodontal tissues, active periodontal lesions are plasma cell rich and may therefore be a source of FLCs. Increased FLC concentrations have been described in a variety of inflammatory and autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, chronic obstructive pulmonary disease and chronic kidney disease (CKD), and were found to be an indicator of early mortality. Our own preliminary data are lending support to the concept that FLCs could also be closely associated with periodontitis and act as a link between periodontitis and systemic diseases by over-activating the immune system.

The Periodontal Research Group at the Birmingham Dental Hospital (UK), has one open PhD position that offers the exiting possibility to investigate FLCs regarding their potential as biomarkers in periodontitis, their biological functions in inflammation and ways to target FLCs in therapy. The PhD project would cover clinical approaches such as measurement of FLCs in patient serum as well as in vitro techniques to establish interactions between FLCs, neutrophils. Strong collaborations with research partners providing expertise and FLC test kits are in place and our laboratory has state-of-the-art equipment available, along with established protocols for cell functional assays. The outcomes of this study will not only be of interest to the periodontal research community, but are also likely to attract interest from other medical fields concerned with chronic inflammation.

Objectives:
There are three main aims within this PhD project:

Firstly, learning existing neutrophil functional assays developed by our group as well as isolation methods and microbiological techniques, for subsequent use in FLC studies.
This will include neutrophil isolation, stimulation with bacteria or bioactive substances and assay of reactive oxygen species, chemotaxis, phagocytosis, neutrophil extracellular trap release and cytokine production.

Secondly, priming and stimulating neutrophils from periodontitis patients and healthy controls with FLCs and (opsonised) bacteria.
This part of the PhD will employ the assays documented in the first section and will involve measuring and isolating FLCs from patients and healthy controls.

Thirdly, investigating the impact of FLCs on the activation of neutrophils by biofilms associated with health, gingivitis and periodontitis.
Host-pathogen interactions will primarily focus on the effects of the biofilms on neutrophils.

Methods/techniques:
Isolation of neutrophils, neutrophil functional assays (NET, reactive oxygen species and cytokine release assays, chemotaxis and phagocytosis assays) including live cell imaging and fluorescence microscopy, chemiluminescence, FACS and ELISA; isolation/separation of FLCs; aerobic and anaerobic microbiology including growth of bacteria in planktonic cultures and biofilms.