What is glomerulonephritis caused by circulating immune complexes?

➢ In circulating immune complex–mediated diseases, the complexes may be formed : ✓With endogenous antigens, as in the GN associated with systemic lupus erythematosus, ✓With exogenous antigens : GN that follows certain bacterial (streptococcal), viral (hepatitis B), parasitic (Plasmodium falciparum malaria), and spirochetal (Treponema pallidum) infections. ✓Often the inciting antigen is unknown, as in most cases of membranoproliferative GN. ➢Once antigen-antibody complexes are deposited or formed in the glomeruli, they produce injury by activating complement and recruiting leukocytes. ➢Morphologically, affected glomeruli exhibit leukocytic infiltrates and variable proliferation of mesangial and parietal epithelial cells ➢EM reveals electron-dense immune deposits in one or more of three locations: 1. Between the endothelial cells and the GBM (subendothelial deposits) 2. Between the outer surface of the GBM and the podocytes (subepithelial deposits), 3. In the mesangium. ➢The localization of antigen, antibody, or immune complexes determines the glomerular injury response