Objectives. The chemokine CXCL13, also known as BCA-1 (B-cell-attracting chemokine-1) or BLC (B-lymphocyte chemoattractant), is a major regulator of B-cell trafficking. We have recently shown that excessive expression of dendritic cell-derived CXCL13 is a distinctive early event for nephritis in a murine model of systemic lupus erythematosus (SLE). Furthermore, in kidney biopsies from SLE patients, CXCL13 protein and mRNA are strongly expressed in B-cell-containing inflammatory lesions. Here, we ask whether serum levels of CXCL13 correlate with disease activity and renal involvement in SLE patients. Methods. CXCL13 was measured in sera obtained from 91 patients with SLE and 40 healthy controls by ELISA methodology. Disease activity was calculated according to the SLE Disease Activity Index (SLEDAI). Results. Median (IQR) serum CXCL13 concentrations were increasingly higher across the following groups: healthy controls [31.6 (26.8–41.3) pg/ml], SLE patients with inactive disease (SLEDAI <6) [68.2 (27.8–133.0) pg/ml, P = 0.0006 versus controls] and active disease [196.0 (75.9–416.8) pg/ml, P = 0.0001 versus controls] (inactive versus active P < 0.0001). Concentrations of circulating CXCL13 correlated with SLEDAI ( r = 0.56, P < 0.0001) and double-stranded DNA titres ( r = 0.36, P < 0.0005). Moreover, median CXCL13 concentrations were higher in patients with renal involvement [175.5 (105.3–422.6) pg/ml] compared to those without renal involvement [82.1 (42.9–219.8) pg/ml]. Conclusions. Our data indicate that increased level of CXCL13 is a feature of SLE that correlates with disease activity. Furthermore, CXCL13 might be a readily available surrogate marker to monitor the extent of aberrant B-cell (dys-)function.

Summary: Podocytes maintain the structure and function of the glomerular filtration barrier. However, podocytes have recently been implicated in the innate immune response, and their function as non-haematopoietic antigen-presenting cells was highlighted. We have shown previously that excessive expression of the chemokine CXCL13 is a distinctive early event for nephritis in a murine model of systemic lupus erythematosus (SLE). Furthermore, we found that CXCL13 is elevated significantly in the serum of patients with SLE-nephritis. In this study, we were able to show for the first time that (i) CXCL13 is expressed locally in glomeruli in a model for SLE-nephritis in mice and that (ii) incubation of human podocytes with CXCL13 induces receptor stimulation of CXCR5 with activation of signalling pathways, resulting in (iii) secretion of proinflammatory cytokines and chemokines in culture supernatant. This cytokine/chemokine cocktail can lead to (iv) a neutrophil respiratory burst in isolated human granulocytes. Taken together, our results provide further evidence that CXCL13 is involved in the pathogenesis of glomerulonephritis and that podocytes can play an active role in local proinflammatory immune responses. Thus, CXCL13 could be a direct target for the therapy of glomerulonephritis in general and for SLE-nephritis in particular.

Follow-up care after kidney transplantation is performed in transplant centers as well as in local nephrologist’s practices in Germany. However, organized integrated care of these different sectors of the German health care system is missing. This organizational deficit as well as non-adherence of kidney recipients and longterm cardiovascular complications are major reasons for an impaired patient and graft survival. The KTx360° study is supported by a grant from the Federal Joint Committee of the Federal Republic of Germany. The study will include 448 (39 children) incident patients of all ages with KTx after study start in May 2017 and 963 (83 children) prevalent patients with KTx between 2010 and 2016. The collaboration between transplant centers and nephrologists in private local practices will be supported by internet-based case-files and scheduled virtual visits (patient consultation via video conferencing). At specified points of the care process patients will receive cardiovascular and adherence assessments and respective interventions. Care will be coordinated by an additional case management. The goals of the study will be evaluated by an independent institute using claims data from the statutory health insurances and data collected from patients and their caregivers during study participation. To model longitudinal changes after transplantation and differences in changes and levels of immunosuppresive therapy after transplantation between study participants and historical data as well as data from control patients who do not participate in KTx360°, adjusted regression analyses, such as mixed models with repeated measures, will be used. Relevant confounders will be controlled in all analyses. The study aims to prolong patient and graft survival, to reduce avoidable hospitalizations, co-morbidities and health care costs, and to enhance quality of life of patients after kidney transplantation. ISRCTN29416382 (retrospectively registered on 05.05.2017)

Chemokine CXC ligand 13 (CXCL13) has been implicated in perivascular inflammation and pulmonary vascular remodeling in patients with idiopathic pulmonary artery hypertension (IPAH). We wondered whether CXCL13 may also play a role in chronic thromboembolic pulmonary hypertension (CTEPH) and whether serum levels of CXCL13 might serve as biomarkers in these conditions. Lung tissue from patients with IPAH or CTEPH was immunostained for CXCL13. Serum samples were obtained from patients with IPAH (n = 42) or CTEPH (n = 50) and from healthy controls (n = 13). Serum CXCL13 concentrations were measured by enzyme-linked immunosorbent assay technology and were evaluated for associations with markers of disease severity and survival. CXCL13 was expressed in pulmonary vascular lesions and lymphocytes of patients with IPAH and inoperable CTEPH, respectively. Serum CXCL13 was elevated in patients compared to healthy controls [median, interquartile range, 83 (55,114) pg/ml versus 40 (28, 48) pg/ml; p < 0.001]. Serum CXCL13 showed only weak and inconsistent correlations with markers of inflammation or disease severity. In both populations, patients with serum CXCL13 above the median of the respective groups did not have a higher risk of death than patients with lower serum CXCL13. CXCL13 was overexpressed in pulmonary vascular lesions of patients with IPAH and CTEPH, and increased serum concentrations were found in patients with IPAH and CTEPH, suggesting a potential pathogenic role of CXCL13 in both diseases. However, given the weak associations between serum CXCL13 and markers of disease severity and outcome, CXCL13 is unlikely to become a promising biomarker in these patient populations.

Recent studies have demonstrated that CXCL13 serum levels correlate significantly with systemic lupus erythematosus (SLE) disease activity. However, experimental studies show that CXCL13 production can also be induced by bacterial exposure as well as in response to inflammatory cytokines. This report asks whether CXCL13 serum levels are elevated in patients with evidence of bacterial infections and whether there is a correlation with the C-reactive protein (CRP) levels or the severity of illness in critically ill patients. CXCL13 levels were compared in 39 patients with active SLE (without concomitant infection), 40 non-SLE patients with sepsis, and 40 healthy controls by enzyme-linked immunosorbent assay (ELISA) methodology. We also tested storage conditions and freeze–thaw cycles for stability of CXCL13 in serum samples. Our studies demonstrated that the median CXCL13 serum levels were significantly elevated in patients with SLE [median 83 pg/ml (interquartile range 38–366)] or sepsis [359 pg/ml (151–459)] compared with healthy controls [32 pg/ml (27–41), p < 0.001]. The CXCL13 serum levels correlated with disease activity in SLE (CXCL13 vs. SLEDAI r = 0.65, p < 0.001), but were not associated with severity of illness score in critically ill patients (CXCL13 vs. SOFA r = −0.15, p = 0.35). However, CXCL13 serum levels were clearly associated with CRP levels in both sepsis (r = 0.45, p = 0.003) and SLE (r = 0.39, p = 0.02). In conclusion, CXCL13 is a stable serum marker for disease activity in SLE patients, but concomitant infections can also lead to increased CXCL13 levels.