B-Cell-Attracting Chemokine CXCL13 As a Marker of Disease Activity in Systemic Lupus Erythematosus (SLE)

Abstract

Background A correlation was detected between the chemokine CXC ligand 13 (CXCL13) and lupus nephritis, but there is no data recorded in the literature about a relationship with other disease manifestations in systemic lupus erythematosus (SLE). Therefore, we sought to investigate the relationship between CXCL13 and overall disease activity and other disease manifestations in SLE. Patients and Methods Fifty-seven SLE patients (51 female, 6 male) aged 18–60 years, fulfilling≥4 SLICC classification criteria for the classification of SLE, were enrolled in a cross-sectional study. Disease activity was scored using the SLE Disease Activity Index (SLEDAI) scoring system. The serological workup included routine lab investigations (full blood count, liver and kidney function tests, and urinalysis) as well as ESR, CRP, anti-ds DNA, C3, C4, 24-h urine protein, and creatinine clearance. Plasma CXCL13 levels were detected by ELISA. Results CXCL13 levels were elevated in active SLE patients. A significant positive correlation was found between the total score of SLEDAI and CXCL13 levels (r=0.547, p-value <0.0001). A statistically significant difference was found regarding the mean CXCL13 levels between the patient groups (classified according to SLEDAI score) (inactive <3, mild/moderate ≥3–12, severe ˃12) (p-value<0.001). The anti-ds DNA antibody titre showed a significant positive correlation with CXCL13 levels (r=0.335, p-value<0.05). The complement levels (C3, C4) showed a significant negative correlation with CXCL13 levels (p-value<0.001). Also there was a significant positive correlation between 24-h urine protein and urinary casts and CXCL13 levels (p-value<0.05). Conclusion Our study revealed elevated levels of serum CXCL13 in active SLE patients. We demonstrated a highly significant positive correlation between serum CXCL13 levels in active SLE patients and SLE disease activity, which supports the role of CXCL13 in the pathogenesis of SLE disease and its activity. Among the variants used in calculating the SLEDAI score, we detected significant relations between level of serum CXCL13 and each of total and extra-renal SLEDAI score.