The aim of this research project is to better understand the origin and clinical significance of two lupus-specific "genetic signatures" (IFN signature and plasma cell signature) in patient subgroups with well-defined clinical characteristics. Our aim is to correlate these genetic signatures with cell activation profiles and the production of specific cytokines in different populations from whole blood and in short-term cultures of these circulating cells.

The aim of the experiment is, on the one hand, to identify and study the different cell populations from whole blood by flow cytometry and, on the other hand, to assay different cytokines in blood and urine samples from diseased (SLE) and control subjects (with non-inflammatory rheumatic diseases) in order to highlight and correlate the presence of biomarkers to disease activity or to a clinical manifestation of the disease.

In vitro studies will also be carried out on short-term cultures of PBMCs (Peripheral Blood Mononuclear Cells).

Inclusion Criteria:

• Fulfilment of the EULAR/ACR classification criteria of SLE.
• 18 years of age or above.
• Incident or Flare biopsy-proven proliferative or membranous LN

Exclusion Criteria:

• Antiphospholipid syndrome nephropathy (APSN).
• Pregnancy at baseline (pregnancy during follow-up will not lead to exclusion).
• Anticipated non-adherence to therapy.
• Medical conditions interfering with outcome evaluations.
• Inability to read and/or sign the informed consent form.

Incident or Flare biopsy-proven proliferative or membranous LN diagnosis