Human IgA nephritis: immunocytochemical evidence of a chronic inflammatory proliferative disorder.

This overview summarizes recent information concerning the biopathology of mesangial cell proliferation and matrix expansion which constitute fundamental features in human IgA nephritis. The currently available knowledge, mainly stemming for immunohistochemical observation of human materials, experimental investigations with laboratory animals, and mesangial cell culture studies, emphasizes the importance of cell to cell, cell to soluble factors, and cell to matrix interactions. Mesangial cells, activated by cytokines and growth factors, express adhesion molecules, stimulate proliferation both of themselves and neighbouring cells, and synthesize extracellular matrix. Matrix components, in turn, may influence the behaviour and proliferation activity of mesangial cells, or act as a receptor or reservoir for growth factors. Expression of protooncogenes, regulating cell proliferation and apoptosis, by glomerular cells could be associated with persistent cell replication and chronic tissue damage. These disease processes seem to be common to a group of diseases termed chronic inflammatory proliferative disorders.