Studies on the role of the lpr gene in the development of immunological abnormalities and lupus nephritis. Analyses in F2 mice.

In order to clarify role of lpr gene of MRL/Mp-lpr/lpr (MRL/l) mice in the development of immunological abnormalities and lupus nephritis, F2 mice were obtained from crosses of (MRL/1 X AKR) F1 mice and examined with regard to lymph node enlargement, numbers of immunoglobulin (IgM and IgG) producing cells (PC) in the spleen, serum levels of anti-trinitrophenyl (TNP) and anti-DNA antibodies, amounts of circulating immune complexes (IC) and histopathological findings of the kidney. Out of total numbers of 234 F2 mice, 54 mice (F2[+]mice) (23.1%) were with lymphoproliferation and 180 mice (F2[-]mice) (76.9%) without it. As parental controls, 39 MRL/1, 27 AKR and 21 F1 mice were also checked. There were significant differences in the all of the parameters tested between F2 (+) and F2 (-) mice. Significant differences were also observed between F2 (+) and MRL/l mice in the weight of mesenteric lymph nodes, numbers of IgGPC, levels of IgG antibodies and amounts of IC, but not in the numbers of IgMPC and levels of IgM antibodies. All of F1 mice tested mimicked AKR mice in the values of various parameters described above. In MRL/l and F2 (+) mice, there were no significant correlations between the weight of mesenteric lymph nodes and other parameters. These data seem to show that the lpr gene behaves as a single recessive trait and there exists gene(s) which suppresses expression of the lpr gene.