Studies on the mechanisms of the development of lupus nephritis in BXSB mice. II. Comparative studies between male BXSB and MRL/lpr mice at the onset period.

In order to analyze relation of immunological abnormalities to the development of lupus glomerulonephritis (LGN) at an early stage, various immunological parameters were examined in BXSB and MRL/lpr mice at 8 and 13 weeks of age. The following results were obtained. (a) Male BXSB mice showed slight LGN already at 8 weeks of age and the disease became obvious at 13 weeks of age. On the other hand, glomerular change of MRL/lpr mice became apparent at 13 weeks. (b) Immunofluorescent studies to semiquantify degree of the deposition of immune complexes (IC) at glomeruli revealed that there were no difference in fluorescence intensities among BXSB mice at 8 and 13 weeks and 13-week-old MRL/lpr mice. (c) MRL/lpr mice had much higher level of serum IC than male BXSB mice at 13 weeks as assessed by fluid- and solid-phase C1q-binding assays. Both strains showed almost the same level of Raji cell-binding IC which might be related to glomerular depositing ones. (d) Spleen of 13-week-old MRL/lpr mice contained extraordinary number of IgG-producing cells in spleen as compared with 8-week-old mice or male BXSB mice at 8 or 13 weeks. There were no differences in IgM-producing cell numbers among the strains and ages of mice. These results indicate that MRL/lpr and male BXSB mice have different immunological backgrounds for the development of LGN. It was noticeable that male BXSB mice showed some degree of LGN already at 8 weeks of age, without apparent polyclonal B cell activation and enhanced serum level of IC, as compared with MRL/lpr mice of the same age.