Commensal microbiota are critical for the development of local immune responses. In this article, we show that gut microbiota can regulate CD4 T cell polarization during pulmonary fungal infections. Vancomycin drinking water significantly decreased lung Th17 cell numbers during acute infection, demonstrating that Gram-positive commensals contribute to systemic inflammation. We next tested a role for RegIIIγ, an IL-22–inducible antimicrobial protein with specificity for Gram-positive bacteria. Following infection, increased accumulation of Th17 cells in the lungs of RegIIIγ−/− and Il22−/− mice was associated with intestinal segmented filamentous bacteria (SFB) colonization. Although gastrointestinal delivery of rRegIIIγ decreased lung inflammatory gene expression and protected Il22−/− mice from weight loss during infection, it had no direct effect on SFB colonization, fungal clearance, or lung Th17 immunity. We further show that vancomycin only decreased lung IL-17 production in mice colonized with SFB. To determine the link between gut microbiota and lung immunity, serum-transfer experiments revealed that IL-1R ligands increase the accumulation of lung Th17 cells. These data suggest that intestinal microbiota, including SFB, can regulate pulmonary adaptive immune responses.

Large randomized clinical trials (RCT) supporting guidelines for the management of HFrEF have typically excluded patients with advanced CKD. Patients with concomitant advanced CKD and HFrEF experience poor cardiovascular outcomes and mortality relative to either disease in isolation and have been shown to consistently receive lower rates of HFrEF guideline-directed medical therapy (GDMT). In this review, we evaluate recent evidence for the use of GDMT in patients with HFrEF and advanced CKD approaching dialysis from RCTs and observational cohorts. We also discuss the limitations and challenges inherent in the evidence for GDMT in this population and offer guidance to clinicians for proper clinical use and future research directions.

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