Urinary interleukin 22 binding protein as a marker of lupus nephritis in Egyptian children with juvenile systemic lupus erythematosus

Juvenile systemic lupus erythematosus (JSLE) is a multi-system autoimmune inflammatory disease. Generally, 60% of patients will develop lupus nephritis (LN); thus, early recognition and treatment is associated with better outcome. Interleukin 22 (IL-22) is involved in tissue inflammation and is regulated by interleukin 22 binding protein (IL-22BP). This study aimed to use IL-22BP as a non-invasive marker for disease activity in JSLE and LN. This is a cross-sectional study conducted on 82 subjects: 51 JSLE patients and 31 healthy controls of matched age and gender. Urinary IL-22BP was measured using enzyme-linked immunosorbent assay, and its level was correlated with different clinical and laboratory data in JSLE as well as Systemic Lupus Erythematous Disease Activity Index 2000 (SLEDAI-2k), renal SLEDAI-2k, and Systemic Lupus International Collaborating Clinics (SLICC) renal activity score which were used to assess overall disease and renal activity. Our results showed that urinary IL-22BP level was significantly higher in JSLE patients with mean level of 4.13 ± 1.10, as compared to controls 1.63 ± 0.61 (P value < 0.001); also, patients with active LN had urinary levels of IL-22BP (5.47 ± 1.03) higher than patients with active JSLE without LN (4.23 ± 0.72) and patients with non-active JSLE/LN (3.5 ± 0.65) with a highly significant P value < 0.001. There was a positive correlation with SLEDAI-2k, renal SLEDAI, and renal activity scores (P < 0.001). Urinary IL-22BP may be used as a non-invasive marker for assessment of disease activity in children with JSLE and LN.