Based on the observation that macrophage infiltration is important in the pathogenesis of glomerulonephritis in AAV, Tam et al. investigated urinary monocyte chemoattractant protein 1 (MCP-1), and fractalkine as potential non-invasive biomarkers for renal vasculitis in adults with AAV [44]. The gene discussed is CX3CL1; the disease is anti-neutrophil cytoplasmic antibody-associated vasculitis.