The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular-or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m 2 in 30-to 34-year-old men and 83 ml/min/1.73 m 2 in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age-and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.

The opportunistic nosocomial pathogen Clostridioides difficile exhibits phenotypic heterogeneity through phase variation, a stochastic, reversible process that modulates expression. In C. difficile, multiple sequences in the genome undergo inversion through site-specific recombination. Two such loci lie upstream of pdcB and pdcC, which encode phosphodiesterases (PDEs) that degrade the signaling molecule c-di-GMP. Numerous phenotypes are influenced by c-di-GMP in C. difficile including cell and colony morphology, motility, colonization, and virulence. In this study, we aimed to assess whether PdcB phase varies, identify the mechanism of regulation, and determine the effects on intracellular c-di-GMP levels and regulated phenotypes. We found that expression of pdcB is heterogeneous and the orientation of the invertible sequence, or ‘pdcB switch’, determines expression. The pdcB switch contains a promoter that when properly oriented promotes pdcB expression. Expression is augmented by an additional promoter upstream of the pdcB switch. Mutation of nucleotides at the site of recombination resulted in phase-locked strains with significant differences in pdcB expression. Characterization of these mutants showed that the pdcB locked-ON mutant has reduced intracellular c-di-GMP compared to the locked-OFF mutant, consistent with increased and decreased PdcB activity, respectively. These alterations in c-di-GMP had concomitant effects on multiple known c-di-GMP regulated processes, indicating that phase variation of PdcB allows C. difficile to coordinately diversify multiple phenotypes in the population to enhance survival.

Objectives. T regulatory cells (Tregs) are a heterogeneous group of immunoregulatory cells that dampen self-harming immune responses and prevent the development of autoimmune diseases. In anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis, Tregs possess diminished suppressive capacity, which has been attributed to the expression of a FOXP3 splice-variant lacking exon 2 in T cells (FOXP3D2 CD4 + T cells). However, the suppressive capacity of Tregs varies between subsets. We evaluated the frequency of Treg subsets in ANCA vasculitis as a potential explanation for diminished suppressive capacity. Methods. We developed a custom mass cytometry panel and performed deep immune profiling of Tregs in healthy controls, patients with active disease and in remission. Using these data, we performed multidimensional reduction and discriminant analysis to identify associations between Treg subsets and disease activity. Results. Total Tregs were expanded in ANCA vasculitis, which was associated with remission and the administration of rituximab and/or prednisone. The frequency of FOXP3D2 CD4 + T cells did not distinguish disease activity and this population had high expression levels of CD127 and lacked both CD25 and Helios, suggesting that they are not conventional Tregs. The frequency of CXCR3 + , CD103 + and CCR7 + Tregs distinguished disease activity, and the combination of the frequency of these three Treg subsets segregated active patients from patients in remission and healthy controls. From these three subsets, the frequency of CXCR3 + Tregs distinguished patients with active disease with renal involvement. Conclusion. Treg heterogeneity can discriminate disease activity and should be explored as a biomarker of disease activity in ANCA vasculitis.

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