Very little is known about the initial subendothelial localization of immune complexes in glomeruli. Using human glomerular endothelial cell lines established in this laboratory, cells will be evaluated for transcytosis of immune complexes of human serum albumin and anti-human serum albumin (HSA). In order to determine whether immune complex interaction with glomerular endothelial cells is an active or passive process, three methods will be employed. First, using radiolabeled immune complexes dose response curves will be obtained testing for the presence of saturation kinetics. Second, endothelial cell-immune complex interaction will be followed using video enhanced fluorescence microscopy. Third, complexes and endothelial cells will be evaluated by immunoelectron microscopy.