Effects And Mechanisms Of TACI-Ig On Mice With Collagen-induced Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that T and B lymphocytes and various pathogenic factors involved together. B lymphocyte stimulator (BLyS) plays an important role in B lymphocyte maturation and survival. Extensive research proves that overexpression of BLyS is closely involved in the pathogenesis and progression of autoimmune disorders such as RA. The level of BLyS is high in serum and synovia of RA patients, and synovia BLyS is higher than serum. Transmembrane activator and calcium modulator cyclophilin ligand interactor (TACI) is one of the receptors of BLyS, which can be found on B cells and activated T cells. TACI-Ig is a soluble glycoprotein comprised of a human IgG1-Fc fused with the extracellular domain of the human TACI receptor, which can block B cell activation that BLyS mediated, by binding with BLyS competitively. In the current study, collagen-induced arthritis (CIA) models were established in DBA/1 mice to investigate the therapeutic effects and mechanisms of TACI-Ig on CIA mice.Objective:Research the therapeutic effects and effective dose of TACI-Ig on CIA mice initially. Then investigate the characteristics of effects and mechanisms of TACI-Ig on CIA mice in further study.Methods:CIA models were established in DBA/1 mice; evaluation of arthritis scores; histopathology examination and pathology scores of joints and spleens; indices of thymus and spleen assay; B and T lymphocytes proliferations assayed by [3H]-TdR method; serum BLyS, IgA and IgM assayed by ELISA; expression of CD20 in spleen tissue of CIA mice assayed by immunohistochemistry; the percentage of CD19~+, CD19~+IgD~+, CD19~+CD27~+, CD19~+IgM~+, CD19~+CD21~+ and CD19~+CD23~+ cells in spleen assayed by flow cytometry; the percentage of CD3~+CD4~+, CD4~+CD154~+, CD4~+CD25~+, CD4~+CD69~+ and CD4~+CD62L~+ cells in thymus assayed by flow cytometry; B lymphocytes and T lymphocytes of CIA mice were co-cultured with Transwell cell culture system, then B and T lymphocytes proliferations were assayed by MTT method.Results:1. Exploration of the effective dose of TACI-Ig on CIA miceTACI-Ig (3.333, 10 and 30mg/kg, intraperitoneal injection, three times per week, treat 6 weeks) could reduce the arthritis score, ameliorate the changes of paws radiology, as well as the changes of joints and spleens histopathology in CIA mice, reduce the increased indices of thymus and spleen, inhibite B and T lymphocytes proliferation response, and reduce the increased serum level of BLyS in CIA mice. However, there was no significant difference between TACI-Ig (10 mg/kg) group and TACI-Ig (30 mg/kg) group. TACI-Ig (1.105 mg/kg) only reduced the increased serum level of BLyS in CIA mice. TACI-Ig (0.35 mg/kg) had no obvious effect on these above-mentioned indices.It indicated that TACI-Ig has a good effect on CIA mice, and the best dose of TACI-Ig mainly between 3.333 and 10 mg/kg,which provide a dosage range for further study of the therapeutic effects and mechanisms of TACI-Ig on CIA mice.2. The characteristics of therapeutic effects of TACI-Ig on CIA miceTACI-Ig (3 and 9 mg/kg, subcutaneous injection, three times per week, treat 6 weeks) could reduce the arthritis scores of CIA mice; reduce the histological pathology scores of synovial hyperplasia, cell infiltration, pannus, inflammation and bone erosion of joints in CIA mice, and reduce the histological pathology scores of cell density lymphatic sheath, lymphoid follicular hyperplasia, marginal zone and red pulp, as well as the number of germinal center. TACI-Ig (1mg/kg) only reduced the histological pathology scores of synovial hyperplasia, cell infiltration, pannus and inflammation of joints in CIA mice, and reduced the histological pathology scores of cell density lymphatic sheath. However, there was no obvious effect of these treatment groups on the depressed weight of CIA mice.3. TACI-Ig could inhibit the function of B and T lymphocytes, and regulate the changes of B and T lymphocytes subsets in CIA mice.TACI-Ig (1, 3 and 9 mg/kg, subcutaneous injection, three times per week, treat 6 weeks) could reduce indices of thymus; degrade the percentage of CD19~+, CD19~+IgD~+, CD19~+IgM~+ and CD19~+CD21~+ cells in spleen of CIA mice; degrade the percentage of CD4~+CD154~+ and CD4~+CD69~+ cells in thymus of CIA mice; heighten the percentage of CD4~+CD62L~+ cells. TACI-Ig (3 and 9 mg/kg) could reduce indices of spleen of CIA mice; inhibit B and T lymphocytes proliferation response in CIA mice; reduce the serum level of BLyS and IgA; inhibit the positive expression of CD20 in spleen tissue of CIA mice; degrade the percentage of CD19~+CD23~+ cells. Only TACI-Ig (9 mg/kg) could reduce the increased serum level of IgM in CIA mice, and degrade the percentage of CD4~+CD25~+ cells. However, there was no obvious effect of these treatment groups on the percentage of CD19~+CD27~+ and CD3~+CD4~+ cells. Results showed that B and T lymphocytes of CIA mice had a stimulative effect on proliferation to each other. TACI-Ig (100μg/ml) could inhibit the interaction of B and T lymphocytes in vitro. It indicated that mechanisms of TACI-Ig on CIA mice might be related to the inhibition of the function of B and T lymphocytes, and the regulation role on the subsets of B and T lymphocytes in CIA mice.Conclusion:1. TACI-Ig has a therapeutic effect on CIA mice, and the best dose of TACI-Ig mainly between 3.333 and 10 mg/kg.2. The characteristics of therapeutic effects of TACI-Ig on CIA mice mainly shows in that TACI-Ig could reduce the arthritis scores of CIA mice, and reduce the histological pathology scores of joints and spleens in CIA mice, but has no obvious effect on the weight of CIA mice.3. Mechanisms of TACI-Ig on CIA mice might be related to the inhibition of the function of B and T lymphocytes, and the regulation role on the subsets of B and T lymphocytes in CIA mice.