Material and methods
Study population
In this cross-sectional study, 13 patients with biopsy-verified IgAN and 13 patients with autosomal dominant polycystic kidney disease (ADPKD), as disease controls were recruited. The IgAN and ADPKD patients were matched for kidney function (estimated glomerular filtration rate, eGFR, ±10 ml/min/1.73 m2), gender and age (±10 years). All study participants were recruited from the Department of Nephrology at Danderyd University Hospital in Stockholm, Sweden, and submitted written informed consent. Patients did not have any intercurrent illnesses and had stable treatment (i.e. no change in dose of angiotensin converting enzyme inhibitor (ACE-I) or angiotensin receptor blocker (ARB) within eight weeks from sampling). None of the IgAN patients had a history of macroscopic hematuria. Proteinuria was measured as urine albumin creatinine ratio (UACR). Exclusion criteria were ongoing treatment with systemic corticosteroids or other systemic immunosuppressive drugs, treatment with systemic corticosteroids within six months from sample draft, diabetes mellitus, neoplasms or other inflammatory diseases. Healthy controls (HC) (n = 13) were recruited by announcement and were gender- and age-matched (±5 years) with IgAN patients. Demographic characteristics of participants are presented in Table 1.