Studies on the Mesangial Handling of Protein Antigens: Influence of Size, Charge and Biologic Activity

The influence of certain physicochemical and biologic properties of protein antigens on their handling by the glomerular mesangium was studied in rats. The following ferritin-based probes were employed: (a) naturally occurring ferritin isomers to examine the role of molecular size; (b) chemically cationized ferritins (pI 7.1 and 8.8) to test charge effects; (c) glutaraldehyde (GA-)coupled ferritin as an analogue of a toxic molecule. Molecular size was found to be a major determinant of the extent and rapidity of antigen uptake, but had only a minor influence on persistence. The rapidity of uptake and antigen persistence was charge dependent, but to a limited extent. Biologic activity of macromolecules appears to be a very important determinant of mesangial handling since GA-treated ferritin was taken up much more rapidly and to a greater extent than native ferritin, and could persist for very prolonged periods.