INCREASED LEVELS OF INTERLEUKIN-22 IN END STAGE RENAL DISEASE AND PATIENTS AND ROLE OF DIALYSIS

Introduction and Aims: Interleukin (IL)-22 is a member of the IL-10 cytokine family. The main biological role of IL- 22 includes the increase of innate immunity, antimicrobial defence, protection from damage, and enhancement of regeneration. Patients with end-stage renal disease (ESRD) exhibit immune dysregulation, but the precise immunological profile and the effect of hemodialysis (HD) on it, has not been clearly investigated. Methods: We evaluated IL-22 serum levels in 33 patients (19 females and 14 males, mean age 69±11 years) suffering from chronic renal failure before and after dialysis. We also evaluated IL-22 serum levels in 28 healthy age-sex-matched subjects recruited as controls. Each subject gave a written informed consent to the study. Laboratory measurements: Serum samples were obtained using a serum separator tube and allowing samples to clot for 30 minutes before centrifugation (15 minutes at approximately 1000 x g); serum aliquots were stored at -20° C until the assay.IL-22 serum concentrations were measured by a uantitative enzyme immunoassay technique. The assay was performed by using a commercially available kit (R&D Systems Europe, Abingdon, UK); a microplate reader (BioRad Laboratories, Model 550, Milan) capable of measuring absorbance at 450 nm (correction wavelength set at 540 nm) was used to measure the intensity of colour developed in each well. All samples were analyzed in duplicate. Results: IL-22 serum levels were significantly higher in patients (26.32 ±22.77 vs.10.66±5.84; p<0.0001) and after dialysis (28.82±23.12 vs.10.66±5.84; p<0.0001). An increase was documented also after dialysis (26.32 ±22.77 vs. 28.82±23.12; p=0.002), IL22 after dialysis grew in 28 and decreased in 5 patients. The dialysis technique, diffusive (BIC) or convective (AFB, HFR, HDF) did not affect IL22 levels (24.64 ±12.41 vs.29.25±28.11; p=0.982). Conclusions: IL-22 can play either a protective or a pathogenic role in chronic inflammatory diseases depending on the nature of the affected tissue and the local cytokine milieu. Our study showed significantly altered T cell-associated immunity in these subjects compared to controls, which is not related or influenced by the type of dialysis.