#1980 Past peritonitis episodes are linked to decreased peritoneal Immune Cell Function and Associated with Chronic Increased Peritoneal Inflammation
Authors: Herzog Rebecca , Daniel-Fischer Lisa , Eibensteiner Fabian , Vychytil Andreas , Aufricht Christoph , Kratochwill Klaus 
Published: May 2024

Abstract

Background and Aims
Chronic peritoneal inflammation and infectious complications occur in a significant proportion of PD patients. A relationship between peritoneal IL-6 levels and local immunocompetence is suspected. To analyse local immunocompetence, an ex-vivo stimulation assay of PD effluent was developed. The aim of this study was to analyse peritoneal inflammation and immunocompetence in a PD cohort in relation to clinical outcomes.

Method
Prospectively, 245 routinely performed 4-hour PETs (143 patients, 2679 patient-months) of patients exclusively receiving 2. generation PD fluids (two-chamber, pH neutral, low amount of glucose degradation products) were analysed. An ex-vivo cell stimulation protocol of the fresh effluents was performed of all PETs. Peritoneal immune cell function was analysed using ex-vivo Toll-like receptor (LPS/Pam3Cys) stimulated IL-6 release as an index of immunocompetence. The molecular effects of effluent components and the addition of alanyl-glutamine to PD fluid were analysed in heterologous cell stimulation experiments and using an effluent proteomics and metabolomics approach.

Results
IL-6 in the effluent showed no association with various patient characteristics (incl. RRF, underlying disease, peritonitis episodes, time on PD). A significant association of peritoneal IL-6 with solute transport rates and systemic markers of uremic inflammation was found. IL-6 in effluent (HR 2.54) and stimulated 1 h effluent (HR 0.34) was predictive of subsequent peritonitis episodes. An inverse association was observed with ex-vivo stimulated IL-6 release from peritoneal cells (P = .02), most pronounced in patients with a history of peritonitis (P = .008). Patients with above median elevated IL-6 levels showed reduced peritoneal immune cell function. The results were validated in an independent multi-centre PD cohort (n = 48). A proteomics (n = 17) and targeted metabolomics (patients n = 134, 1004 metabolites) analysis of PD effluents show an overrepresentation of apoptosis and neutrophil degranulation pathways in patients with elevated effluent IL-6 levels and reduced response mechanisms to pathogens when compared to effluents from patients with low effluent IL-6 levels. Heterologous donor-PBMC stimulation (4 Healthy donors) with 4h PET PD-effluents of 20 patients showed reduced immunocompetence with elevated IL-6 (P = .038) and improved immunocompetence when 8 mM alanyl-glutamine were added to the PD fluid during the dwell. These results could also be validated in a post-hoc analysis of a RCT testing alanyl-glutamine addition to PD fluid for 8 weeks in PD patients.

Conclusion
This is the first longitudinal study to show the relationship between peritoneal inflammation and impaired immune function of peritoneal cells, possibly predisposing to infectious complications. The possible underlying mechanistic link may represent the biological correlate (“immune-paralysis”) for PD patients at increased risk for recurrent episodes of peritonitis.