Background: Systemic Lupus Erythematosis (SLE) is a chronic inflammatory multi-systemic disorder of the connective tissue, characterized by the production of a wide range of auto-antibodies mainly directed to nuclear antigens and immune complexes that may lead to tissue injuries. Interleukin 15 (IL-15) is a Th1 cytokine that is produced by cells and has been expressed by activated monocytes/macrophages.

The aim is to evaluate the serum and peripheral blood mononuclear cells (PBMCs) levels of IL-15 in SLE patients, also in the PBMCs before and after stimulation by lipopolysaccharides (LPS), and its relation to the state

of disease activity and morbidity in SLE patients.

Patients and Methods: Thirty patients with SLE fulfilling the American College Criteria (ACR) for diagnosis of the disease, and twenty healthy normal subjects as a control group for IL-15 in serum & PBMCs were enrolled in the study.

Patients were assessed clinically. Evaluation of the disease activity state was done by using systemic lupus disease activity index (SLEDAI), and disease damage was evaluated by applying the SLE disease damage index (SLEDDI). Laboratory investigations included: complete blood picture,

serum urea and creatinine, erythrocyte sedimentation rate (ESR), Creactive protein (CRP), anti-nuclear antibodies (ANA), anti- native DNA (Anti-ds-DNA) and complement 3 and 4 (C3, C4). IL-15 levels in serum and the culture supernatant of PBMCs before and after stimulation by LPS

were measured using ELISA technique.

Results: The mean value of serum IL-15 in SLE patients was significantly higher than in the healthy group and there was a positive significant correlation between serum IL-15 in SLE patients and total SLEDAI score.

Also, there was a significant increase in IL-15 serum level of SLE patients presenting clinically with fatigue, alopecia, arthralgia, arthritis or vasculitis. This can also be applied to the serum level of ESR, CRP, ANA and anti-ds DNA. Yet, there was no significant difference between the

mean value of IL-15 IN PBMCs culture supernatant in SLE patients and the control group either before or after induction by LPS.

Conclusion: In SLE IL-15 can positively reflect the state of disease activity as it shows a good correlation with some clinical and laboratory parameters of disease relapse, and is in part responsible for some immunological abnormalities seen in patients.