| Abstract: | Summary: Most glomerular diseases are autoimmune in nature with injury occurring as a consequence of antibody reacting with antigens on glomerular cell membranes or in glomerular matrix, or immune complex formation occurring on or near glomerular cell membrnes. Many of the structural and functional consequences of these events result from the response of resident glomerular cells to the injury, or may be induced by inflammatory effector cells derived from the circulation. In terms of glomerular cells, injury to the glomerular epithelial cell (GEC) may be induced by: (i) non-complement fixing antibodies which mimic the glomerular lesions of minimal change nephrotic syndrome/focal glomerular sclerosis; or (ii) by antibodies which fix complement leading to GEC attack by C5b-9 resulting in a lesion analogous to membranous nephropathy. C5b-9 also mediates antibody induced injury to the mesangial cell resulting in a mesangioproliferative glomerulonephritis (IgA nephropathy, systemic lupus erythematosus; SLE) as well as to the glomerular endothelial cell (thrombotic microangiopathy, haemolytic uraemic syndrome). the effects of C5b-9 may be lytic (mesangial cell, glomerular endothelial cell; GEN) or sublytic (GEC) resulting in stimulation of local oxident and protease production. Both lytic and sublytic effects are substantially modulated by cell-bound complement regulatory proteins such as CD59 and Crry. When fixed or planted antigens are present in larger quantities and accessible to the circulation, complement activation generates chemotactic factors leading to neutrophil infiltration and producing injury through the myeloperoxidase (MPO)-H2-O2-halide system, a mechanism substantially augmented by platelet-neutrophil interaction (post-infectious glomerulonephritis GN], SLE). Macrophages may also be localized in glomeruli by either immune adherence mechanisms or as a consequence of cell mediated immune reactions in the glomerulus. Macrophages differ from neutrophils in producing large amounts of transforming growth factor-β (TGF-β) and procoagulants which contribute to crescent formation rapidly progressive glomerulonephritis (RPGN). |
