MAIT cells altered phenotype and cytotoxicity in lupus patients are linked to renal disease severity and outcome.

Introduction: Systemic lupus erythematosus (SLE) is an autoimmune disease in which circulating immune complexes can cause different types of glomerulonephritis, according to immune deposits and to the type of glomerular cell injury. Proliferative lesions represent the most severe form of lupus nephritis (LN) and often lead to kidney failure and death. Mucosal-associated invariant T (MAIT) cells are a subset of innate-like T cells that recognize microbial-derived ligands from the riboflavin synthesis pathway. Although abundant in peripheral blood, MAIT cells are enriched in mucosal and inflamed tissues. While previous studies have reported concordant results concerning lower MAIT cell frequencies in the blood of SLE patients, no information is known about MAIT cell function and LN severity and outcome. Methods: In the current study, we analyzed the baseline phenotype and function of peripheral blood MAIT cells by flow cytometry in 26 patients with LN and in a control group of 16 healthy individuals. Results: We observe that MAIT cell frequencies are markedly reduced in blood of LN patients. MAIT cells from patients have an altered phenotype in terms of migration, proliferation and differentiation markers, notably in most severe forms of LN. Frequencies of PMA/ionomycin stimulated MAIT cells secreting effector molecules, such as proinflammatory IL-17 and cytotoxic protein granzyme B, are higher in LN patients. Patients undergoing a complete renal remission after immunosuppressive therapy had higher MAIT cell frequency, lower expression of proliferation marker Ki-67 and granzyme B (GzB) at inclusion. Remarkably, GzB production defines a predictive model for complete remission. Discussion: We report here that blood MAIT cells display proinflammatory and cytotoxic function in severe lupus nephritis which may play a pathogenesis role, but without association with systemic lupus activity. Finally, low cytotoxic profile of MAIT cells may represent a promising prognostic factor of lupus nephritis remission one year after induction therapy.

[Middle-molecule uremic toxins: A renewed interest]. / Toxines urémiques de moyen poids moléculaire : un véritable regain d'intérêt.

Cardiovascular mortality in patients with chronic kidney disease remains a major problem. The uremic toxins among which the molecules of middle molecular weight are counted contribute significantly to this high mortality, alongside the traditional risk factors. They generate and maintain a chronic inflammatory state called low-level chronic inflammatory state. A growing interest in these molecules has been noted for some years and the uremic toxins associated with this cardiovascular mortality are currently identified: FGF23, cytokines, pentraxin-3 and recently light chains. The existence of an interaction between uremic toxins, inflammation and/or oxidative stress and cardiovascular mortality is well reported in the various epidemiological studies. While the use of anti-oxidative therapies and/or antibodies against uremic toxins or their site of action have not yet yielded a real benefit, hopes are turning to the use of new hemodialysis membranes medium cut-off (MCO), which have the advantage of purifying the uremic toxin middle molecules without a significant loss of albumin. However, additional works are needed to demonstrate the use of these membranes will lead to modulate the morbi-mortality in the dialysis patients.