Activated Innate Immunity and Involvement of the CX3CR1-FKN Axis in Promoting Hematuria in IgA Nephropathy Patients

The hallmark of IgA nephropathy (IgAN) is gross hematuria (GH) coinciding with or immediately following an upper respiratory or gastrointestinal tract infection and can represent the disease triggering event. Therefore, a whole genomic screening of IgAN patients during the GH was done to clarify the link between mucosal encountered antigens and the occurrence of glomerular hematuria. The modulated genes during GH show a clear involvement of the interferon signalling, antigen presenting pathway, and the immuno-proteasome. The gene characterizing cytotoxic effector lymphocytes (CX3CR1) implicated in vascular endothelial damage, was found up-regulated at both mRNA and protein level. In vitro antigenic stimulation of PBMCs on an independent set of IgAN patients and healthy blood donors (HBS) demonstrated that patients upregulate specifically CX3CR1 in an enhanced and dose dependant manner, while an expected down-regulation occurred in HBD. This enhanced activation occurred in both patients characterized by recurrent GH and by permanent microscopic hematuria (MH). We then analyzed glomerular fractalkine (FKN) expression, since this ligand is involved in the vascular gateway for CX3CR1+ cells towards the inflamed tissues. A significantly higher FKN expression on the capillary vessels and podocytes was found in recurrent GH patients compared to permanent MH, suggesting a predisposition for cytotoxic cell extravasation in recurrent GH patients.

6

Cox SN, Sallustio F, Serino G, Loverre A, Pesce F, Gigante M, Zaza G, Stifanelli PF, Ancona N, Schena FP