Fractalkine associated with disease activity and organ damage in SLE

Recent findings indicate that the soluble form of chemokine fractalkine (sFkn) and its receptor CX3CR1 play a key role in the pathogenesis of systemic lupus erythematosus (SLE).Dr Tsuyoshi Kasama (Showa University School of Medicine, Tokyo) conducted the current study to investigate levels of sFkn and CX3CR1 in SLE patients, its association with neuropsychiatric involvement (NPSLE) and relationship with disease activity and organ damage. To achieve this, serum and cerebrospinal fluid (CSF) were analysed in patients with SLE (n=53), rheumatoid arthritis (RA, n=91) and healthy controls (n=28). These findings were correlated with disease activity and organ damage using the SLE Disease Activity Index (SLEDAI) and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index, respectively.The investigators report that the expression of CX3CR1 was significantly higher in the serum of patients with SLE than those with RA or healthy controls. Also, levels of sFkn were significantly higher in CSF from untreated patients with newly diagnosed NPSLE than in SLE patients without neuropsychiatric involvement. The authors add that treatment reduced both serum and CSF levels of sFkn in patients with SLE.Additionally, serum sFkn levels were positively correlated with disease activity, organ damage, anti-double-stranded DNA and anti-Sm antibody titers, and immune complex levels and were negatively correlated with serum complement activity. As well as an increased expression of sFkn itself, the team also observed increased expression of its receptor (CX3CR1), particularly on CD4+ and CD8+ T cells in patients with active SLE.Reflecting on their findings the authors comment, "in general, the diagnosis of neuropsychiatric complications of SLE is difficult, because no single laboratory marker or imaging modality has been found which can serve as a gold standard, and the diagnosis is thus primarily clinical ... The measurement of sFkn in the cerebrospinal fluid may prove to be a reliable marker for the diagnosis and possibly the follow-up of disease course in these patients."Reference...