| OBJECTIVESystemic lupus erythematosus (SLE)-like mouse model was successfully established by immunizing with active chromatin isolated from concanavalin A (ConA)- activated lymphocytes. We observed the therapeutic effects of B lymphocyte stimulator receptor TACI fusion protein (TACI-Ig) subcutaneously once every other day for 8 weeks on model mice and investigated its partly mechanism.METHODSSLE-like mouse model was successfully established by immunized with active chromatin isolated from ConA-actived lymphocytes. Mice were treated with TACI-Ig (3.75, 7.5, 15mg·kg-1) subcutaneously once every other day from d28 for 8 weeks. General signs were observed. Proteinuria was measured by Semi-quantitative Albustix paper. Histopathological changes of kidney and spleen were observed by haematoxylin and eosine (HE) staining. Thymus index and spleen index were calculated. Thymo-lymphocyte and spleno-lymphocyte proliferation stimulated by ConA and lipopolysaccharide (LPS) were tested by 3H-TdR incorporation method. Levels of Crea and BUN were detected by automatic biochemical analyzer. Levels of ANA, anti-dsDNA, IgG1, IgG2a, BLyS, IL-10 and IFN-γin serum were tested by enzyme-linked immunosorbent assay (ELISA). Splenic T, B lymphocyte subsets were analysed by flow cytometry.RESULTS1. Effect of TACI-Ig on general signs and urine proteinModel mice showed hair loose and glossiness decline from 5-8 weeks, while mice treated with TACI-Ig subcutaneously bahaved actively and had more glossy hair than model group.The level of urine protein of model group gradually improved over time. TACI-Ig (15mg·kg-1) subcutaneously once every other day from 4-8 week and TACI-Ig (7.5mg·kg-1) subcutaneously once every other day from 6-8 week could reduce the level of urine protein of the SLE-like model mice significantly.2. Effect of TACI-Ig on kidney and spleen histopathologyKidney sections from model group showed obvious features of interstitial nephritis, glomerular volume and mesangial matrix increasing, mesangial cell hyperplasia, glomerular hyaline degeneration, local neutrophil infiltration, capillary basement membrane thickening slightly. Spleen sections from model group showed diffuse hyperplasia of the spleen white pulp, central arterial wall fibrous thickening and germinal centers formation. TACI-Ig subcutaneously markedly reduced glomerular volume, decreased mesangial cell hyperplasia, effectively improved renal interstitial hemorrhage, neutrophil infiltration and other inflammatory state. TACI-Ig (7.5, 15mg·kg-1) subcutaneously evidently reduced the formation of splenic germinal centers and improved the hyperplasia of white pulp.3. Effect of TACI-Ig on thymus index and spleen indexSpleen index of model group rose strikingly compared with normal group, but no obvious changes on thymus index were observed. TACI-Ig (15mg·kg-1) subcutaneously could decrease the elevated spleen index of model group significantly.4. Effect of TACI-Ig on thymo-lymphocyte and spleno-lymphocyte proliferationSpleno-lymphocyte proliferation was higher in model group compared with that in control group. TACI-Ig (7.5, 15mg·kg-1) subcutaneously could decrease spleno-lymphocyte proliferation of the model mice stimulated by LPS obviously, but had no significant effect on thymo-lymphocyte proliferation stimulated by ConA.5. Effect of TACI-Ig on renal functionThe levels of Crea and BUN increased significantly in serum of model group compared with control group. TACI-Ig (7.5, 15mg·kg-1) subcutaneously could decrease the elevated levels of Crea and BUN.6. Effect of TACI-Ig on levels of ANA, anti-dsDNA, IgG1 and IgG2a in serumThe levels of ANA, anti-dsDNA, IgG1 and IgG2a increased significantly in serum of model group compared with control group. TACI-Ig subcutaneously could decrease the elevated levels of ANA, anti-dsDNA, IgG1 and IgG2a.7. Effect of TACI-Ig on levels of BLyS, IL-10, IFN-γin serumThe levels of BLyS, IL-10, IFN-γin serum of model group increased obviously. TACI-Ig (3.75, 7.5, 15mg·kg-1) subcutaneously could reduce the level of BLyS evidently. TACI-Ig (15mg·kg-1) subcutaneously could reduce the level of IL-10 markedly. TACI-Ig administration had no significant effect on the level of IFN-γin model mice.8. Effect of TACI-Ig on splenic T, B lymphocyte subsetsThe percentage of total B cells (CD19+), activated B cells (CD19+CD21+, CD19+CD23+) and mature B cells (CD19+IgD+) in spleen elevated significantly in model group compared with control group except immature B cells (CD19+IgM+) and memory B cells (CD19+CD27+). Mice treated with TACI-Ig (3.75, 7.5, 15mg·kg-1) subcutaneously could decrease the percentage of total B cells, activated B cells, mature B cells and immature B cells, but with no significant effect on memory B cells.The percentage of T cell subsets in model group had no significant differences compared with control group. TACI-Ig (15mg·kg-1) subcutaneously could elevate the percentage of activated Th cells (CD4+CD25+), but had no significant effect on other subsets of Th cells.CONCLUSIONS1. TACI-Ig subcutaneously had a therapeutic effect on SLE-like mouse model induced by active chromatin. It could improve renal function effectively, reduce the level of urine protein, ameliorate the pathological changes such as interstitial nephritis and spleen hyperplasia of model mice obviously.2. TACI-Ig subcutaneously could decrease the percentage of total B cells, activated B cells and mature B cells effectively and reduce the elevated levels of autoantibodies and inflammatory cytokines evidently, which prompt that its mechanism may be related with the regulation of immune function. |
