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SALT AUGMENTS TH17 CELL RESPONSES IN ANCA ASSOCIATED
VASCULITIS PATIENTS AND IN MODELS OF INFLAMMATORY KIDNEY
DISEASE
INTRODUCTION: Recent evidence has demonstrated a detrimental effect of salt on innate
and adaptive immunity. A raised extracellular concentration of sodium can cause naïve T
cells to differentiate into pathogenic Th17 cells, and alter macrophage phenotype. The kidney
is the main salt transporting organ and Th17 cells are implicated in both glomerular and
interstitial inflammatory disease. The effect of extracellular sodium concentrations on T cell
activation states in renal inflammatory disease is unknown.
AIMS: To determine the effect of increased extracellular sodium concentration on Th17 cell
activation in patients with ANCA associated glomerular disease; to determine if a high-salt
diet worsens renal inflammation in an experimental model of glomerulonephritis; and to
identify intracellular signalling molecules involved in T cell activation in patients with
autoimmune interstitial disease.
METHODS: Peripheral blood mononuclear cells (PBMCs) from 10 patients with ANCA
associated vasculitis (AAV)(7 PR3- and 3-MPO-ANCA) and 7 healthy controls were isolated
and cultured with CD3/CD28 stimulating antibodies and Th17 polarising cytokines
(IL1,IL6,IL21,IL23, TGFβ), in the presence or absence of additional salt (20 and 40mmol
NaCl). Th17 cell frequencies were analysed by FACS.
IL17-YFP tracker mice were subjected to nephrotoxic nephritis (NTN). One group was fed
normal chow (n=4) and the other group high salt (6%) chow (n=5). The percentage of YFP
positive cells infiltrating the kidney was analysed using FACS.
The inflammatory infiltrate in renal biopsy tissue from patients with Primary Sjögren’s
Syndrome associated tubulointerstitial nephritis (pSS TIN) was isolated via laser
microdissection. Fragments were digested into peptides and analysed by liquid
chromatography electrospray tandem mass spectroscopy. Proteins were compared to patients
with drug induced TIN.
RESULTS: The mean percentage of CD4 +IL17-expressing cells in patients with AAV under
standard conditions was 27.6 +/- 10.7%, as compared to 36.1+/- 12.7% with 20mmol NaCl,
and 46.6 +/- 15.0% with 40mmol NaCl (p<0.01); no differences found between MPO- and
PR3-ANCA patients. In healthy controls there was a more variable effect of salt, with a
general upward trend, but overall no significant difference in CD4+IL17 frequencies after
addition of salt (figure A Patients; B Controls).
The median number of CD3+YFP positive cells infiltrating the kidney in normal salt fed
animals was 0.37% (0.08-0.75) compared with 0.80% (0.6-1.1) in those on high salt diet
(p=0.06) (figure C). Many of these cells also expressed IFN-g in both normal and high salt
groups, suggesting a switch of cytokine phenotype. Impact of salt on other disease biomarkers
including renal function is currently being analysed.
Candidate proteins present in pSS but not drug induced TIN infiltrate were serine/threonine
kinases or phosphatases; WNK kinase-1, SPAK, 14-3-3 protein and protein phosphatase 1.
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CONCLUSION: CD4+Th17 cell responses are significantly augmented by additional salt in
patients with ANCA associated glomerular disease, while a high-salt diet leads to greater
Th17 cell renal infiltration in experimental glomerulonephritis. This salt effect may be
mediated by Serine/threonine kinases and phosphatases.
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