Experimental immune complex glomerulonephritis in the mouse with two types of immune complexes.

Immune complex glomerulonephritis was induced in three groups of mice by long-term immunization. Two antigens of similar molecular weight were used. The first group was immunized with ferritin (mol wt 480,000). In altered glomeruli deposits of immune complexes were seen in the subendothelial and subepithelial spaces of the glomerular basement membrane (GBM) and in the mesangium. The immune complex deposits were formed by amorphous matrix with marked dense molecules of ferritin. The second group was immunized with human fibrinogen (mol wt 450,000). The immune complex deposits were present in the intramembranous, subepithelial and subendothelial spaces of the GBM and in the mesangium. These deposits were relatively less electron-dense and had a fine granular structure. The third group of mice were immunized with both ferritin and fibrinogen simultaneously. Two types of deposits situated subendothelially in the GBM and in the mesangium were seen in one animal of this group. One type of deposit resembled structurally the ferritin-antiferritin complex deposits, the other resembled the fibrinogen-antifibrinogen complex deposits. The individual deposits in the GBM and in the mesangium formed discrete homogeneous masses. The two types of deposit were occassionally in direct contact with one another, but were more often completely separate and were never mixed. It can be assumed that in at least some phase of the experiment both types of complex were present in the circulating blood simultaneously. However, since none of the complexes deposited in the GBM or in the mesangium were mixed, it seems probable that each type of complex is deposited separately in the form of "clusters" composed of a single type of complex. The phagocytic activity of mesangial cells of animals with complex glomerulonephritis was not increased when compared with control animals.