S100A9 and glomerulonephritis: Infiltrating macrophages in the glomeruli produce MRP8 and MRP14 proteins and form MRP8/14 complexes in correlation with the severity of inflammatory response and activity of glomerulonephritis, as shown by immunohistochemical analysis of renal biopsies from different forms of glomerulonephritis, some of which include a relatively high portion of juvenile patients [79].