Therapeutic effects of anti-CXCL10 antibody on C protein-induced myositis (CIM) mouse

Abstract

Introduction. CXCL10 (also called interferon-γ-inducible protein 10

IP-10) is a chemokine that plays a critical role in the infiltration of T cell in autoimmune diseases. CXCL10 is reported to be expressed in muscle tissue of polymyositis. Thus, the role of CXCL10 and the effect of CXCL10 blockade were investigated in C protein-induced myositis (CIM), an animal model of polymyositis. Materials and Methods. CIM was induced with human skeletal muscle C protein fragment in 8-week-old female C57BL/6 mice. Immunohistochemistry was performed to detect CXCL10 and CXCR3, the receptor of CXCL10, in muscle tissue. Serum levels of CXCL10 were measured by enzyme-linked immunosorbent assay. Surface markers including CD3, CD4, F4/80, and B220 and other effector molcules in mouse lymph node cells was investigated by flow cytometry. Migration assay of CIM lymph node cells was performed with 5-μm pore transwell system. Mice with CIM were treated with anti-CXCL10 antibody or control antibody from day 8 after the induction of myositis until day 20 every other day and the inflammation in muscle tissue was assessed 21 days after the induction. Results. Immunohistochemistry showed increased expression of CXCL10 and CXCR3 in the inflammatory lesion of muscle in CIM. Especially, CD8+ T cells invading myofiber expressed CXCR3. Serum level of CXCL10 was increased in CIM compared to normal mice (mean ± SD, normal mouse, 14.3 ± 5.3 pg/ml vs. CIM, 368.5 ± 135.6 pg/ml, p < 0.001). Flow cytometry demonstrated localization of T cells in the lymph node of CIM and increased CXCR3 positivity in CD8+ T cells compared to CD4+ T cells in the lymph node cells of CIM (CXCR3+/CD4+ T cell, 23.5 ± 4.7 vs. CXCR3+/CD8+ T cell, 65.9 ± 2.1, n = 6, p < 0.001). Moreover, IFN-γ+ cells were increased among CXCR3+CD8+ T cells compared to CXCR3–CD8+ T cells (CXCR3+CD8+ T cell, 28.0 ± 4.2% vs. CXCR3–CD8+ T cell, 9.5 ± 1.5%, p = 0.016). Migration of lymph node cells was increased in response to CXCL10 (chemotactic index = 1.91 ± 0.45, p = 0.011). After inducing CIM, mice treated with anti-CXCL10 antibody (n = 10) showed less inflammation score in muscles than those with control antibody (anti-RVG1) (n = 10

median [range], anti-CXCL10, 0.75 [0.25-2.00] vs. anti-RVG1, 1.43 [1.125-4.25], p = 0.045). Conclusion. CXCL10 / CXCR3 expression was increased in the inflammation of CIM model and its blockade suppressed inflammation in muscle.