Key messages

What is already known about this subject?

  • Patients with lupus have been reported to have restricted gut microbiome diversity and general patterns of dysbiosis but few patients with active disease have been previously characterised.

What does this study add?

  • Patients with lupus were found to have characteristic patterns of gut microbiome dysbiosis that directly paralleled disease activity.

  • Patients with systemic lupus erythematosus commonly displayed signs of impaired gut barriers that may result in immune exposure to gut commensal bacteria.

  • Intestinal expansions of Ruminococcus gnavus (RG) were directly proportional to overall disease activity and most pronounced in those with lupus nephritis. Lupus faecal samples displayed increases in sIgA-coated RG bacteria. In three independent cohorts, patients with lupus nephritis displayed elevated serum IgG predominantly to RG strain-restricted cell wall lipoglycan antigens.

How might this impact on clinical practice or future developments?

  • Identification of R. gnavus as a candidate pathobiont opens new areas of investigation of the mechanistic basis by which these outgrowths may affect the overall pathogenesis of lupus and the immune complex-mediated pathogenesis of lupus nephritis.

  • These findings may lead to the development of bioassay(s) with prognostic value for the risk of lupus nephritis.