There is substantial clinical and biological intra and inter-patient variability in SLE. Vascular, renal and neurologic deficiency can be organ-threatening or even life-threatening, leading to increased morbidity and mortality.

Thus, biomarkers of disease activity and prognosis are required for regular follow-up of SLE patients.

Implication of Toll-like Receptors (TLRs) in SLE has been extensively studied in mice models and humans. Self nuclear antigens bind to TLRs which are located on the surface of dendritic cells, B-cells, and endothelial cells, leading to production of pro-inflammatory cytokines and pathologic autoantibodies involved in organ dysfunction of SLE patients. Moreover, TLR expression in SLE is significantly higher and significantly correlated with disease activity.

Annexin A2 (ANXA2) is a member of the annexins superfamily which exists as a monomer or heterotetramer and is implicated in several biological processes. Most notably, it binds to ẞ2GP1/anti-ẞ2GP1 antibodies and mediates endothelial cell activation via a TLR4 signaling pathway, highlighting its key role in Antiphospholipid Syndrome (APS) frequently associated with SLE.

ANXA2 is also involved in the physiopathology of SLE. Anti-DNA autoantibodies can bind with ANXA2 expressed on mesangial cells in lupus nephritis. Besides, a french study carried out in Amiens' University Hospital showed that vascular lesions in lupus nephritis were associated with a significant increase in vascular expression of ANXA2.

Inclusion Criteria:

Inclusion criteria for patients :

• Age ≥ 18 years old
• All SLE patients fulfilling the 1997 ACR criteria, followed at the Departments of Internal Medicine and Nephrology at CHU Amiens-Picardie, regardless of clinical status, treatment, and disease activity.
• Written informed consent

Inclusion criteria for control subjects :

• Age ≥ 18 years old
• Written informed consent

The patients will be compared with age- and sex-matched control subjects.

Exclusion Criteria:

• drug-induced lupus erythematosus
• refusal or incapacity to provide a written informed consent