The glomerular mesangium.

The mesangium is more than simply a support structure for glomerular capillary circulation. Mesangial cells respond to various vasoactive mediators and probably contribute to the regulation of mesangial cell contractility and, consequently, glomerular perfusion. The surrounding extracellular matrix contains several glycoproteins and collagens that may affect the immune interactions of antigens and antibodies and may possibly influence the disposition of immune complexes. These properties may modulate the consequences of deposition of IgA-containing immune complexes in the mesangium in patients with IgA nephropathy and the consequent expression of clinical disease.