The intent of the previous discussion has been to acquaint the reader with the recent expanding knowledge in matrix biochemistry and immunopathology as it pertains to the human GBM. However, it must be emphasized that the GBM antigens, which have yet to be characterized, may outnumber those that are currently defined. SDS-PAGE analysis of GBM isolated by detergent solubilization or sonication reveals at least fifteen different polypeptide components [39]. Of a panel of nine monoclonal antibodies developed following immunization of mice with human GBM, eight stain mature and/or fetal GBM by immunofluorescence microscopy, but only two react by ELISA with currently defined components of basement membrane [98]. Furthermore, current understanding of the mechanisms by which matrix macromolecules participate in such human pathological states as diabetic nephropathy, nephrotic syndrome, sclerosis, and immune complex glomerulonephritis is still quite limited. It is obvious that much is yet to be learned and considerably more is to be gained from continued research in this area.