Introduction: This study aimed at determination of circulating soluble interleukin-2 receptor (IL-2 R) alpha in the sera of patients with systemic lupus erythematosus (SLE) and correlating the level of expression of these receptors with the SLE disease activity.
Materials and methods: The study included 55 patients with SLE and 20 healthy volunteers as controls. The following investigations were done: serum complement component 3, complement 4, erythrocyte sedimentation rate, complete blood count, serum creatinine, creatinine clearance, 24-hour urinary protein, urinalysis, and serum soluble IL-2R alpha level. Kidney biopsy was performed and examined with light microscopy for patients with lupus nephritis by a single pathologist blinded to the clinical activity of the disease. The results were analysed in relation to the clinical activity index of systemic lupus activity measure (SLAM).
Results: The study showed that levels of soluble IL-2R alpha were significantly higher in the total group of patients with SLE compared to the controls (P < .001). Furthermore, serum IL-2R alpha levels were significantly higher in patients with lupus nephritis than those without nephritis. There were strong positive correlations between IL-2R alpha levels and the SLAM score, histological activity index, erythrocyte sedimentation rate, and 24-hour urinary protein excretion. Also, significant inverse correlations with complement 3 and packed cell volume was observed (r = 0.738; r = 0.669; r = 0.328; r = 0.705; r = -0.444; r = -0.420, respectively).
Conclusions: Serum soluble IL-2R alpha is a reliable marker of disease activity in patients with SLE and could be used as an indicator of early renal involvement with the possibility of using it for follow-up.