Lupus Nephritis in Autoimmune‐prone NZBxNZW F1 Mice and Mechanisms of Transition of the Glomerular Lesions

The pattern of renal glomerular lesions in systemic lupus erythematosus (SLE)-prone NZBxNZW (B/W) F, mice shows an age-associated transition, as is often seen in human lupus nephritis during the clinical course of the disease. Observations revealed that the earliest lesions were confined to the mesangium associated mainly with IgM deposits, and to a lesser degree with IgG. In mice over 5 months of age, the lesions extended gradually to the capillary wall with fine granular subepithelial deposits of IgG, but not of IgM. The ultimate pattern of the glomerular lesion was one of diffuse proliferation with diffusely distributed deposits of both IgG and IgM in the mesangium and along the capillary wall. Even at this stage, subepithelial deposits were composed of IgG, but not of IgM. The pattern of glomerular deposits of endogenous retroviral envelope glycoprotein gp70, which is highly anionic, virtually coincided with that of IgG. Taking these findings collectively, it is suggested that the progression of glomerular lesions in B/W F, mice depends largely on the age-associated appearance of retroviral gp70 IgG anti gp70 immune complexes in the circulation and their deposition along peripheral subepithelial, and eventually subendothelial areas. Acta Pathol Jpn 41: 1–11, 1991.