Detection of circulating immune complexes in MRL mice with different forms of glomerulonephritis.

Serum levels of circulating immune complexes (CIC) in MRL mice were determined using the 125I-C1q binding test and a conglutinin enzyme assay. The serum 125I-C1q and conglutinin binding capacity were correlated to the development of different forms of glomerulonephritis (GN) detected by light microscopy. The study was carried out with a total of 132 MRL/MpJ-lpr/lpr and MRL/MpJ(-)+/+ mice of different age groups. From the age of 3 months on an enormous elevation of C1q- and conglutinin-binding CIC occurred in MRL/MpJ-lpr/lpr mice, while in MRL/MpJ(-)+/+ mice the mean values of CIC remained low in all age groups studied. The results corresponded to histopathological glomerular findings. In lpr/lpr-mice, from the age of 3 months on, extremely severe proliferative forms of GN occurred. In most cases of +/+(-)mice examined comparatively mild glomerular lesions were found. In serum samples of Han:NMRI and C3H/He mice an increase of conglutinin-binding material was found in certain age groups, while the levels of 125I-C1q binding activity remained low in mice of all age groups studied.