Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


The Role of Innate Immunity in a Model of HRS-Induced Myositis.

Soejima4,  Makoto, Kang1,  Eun Ha, Katsumata2,  Yasuhiro, Gu3,  Xinyan, Clemens3,  Paula, Ascherman3,  Dana

Seoul National University College of Medicine
Tokyo Women's Medical University
University of Pittsburgh
University of Pittsburgh, Pittsburgh, PA

Aim:

The aim of this study was to clarify the contribution of innate immunity in a model of histidyl-tRNA synthetase (HRS)-induced myositis.

Background:

Previous studies have suggested an important role for the autoantigen HRS in the pathogenesis of myositis. While most investigations have focused on the ability of HRS to trigger adaptive immune responses, in vitro studies clearly indicate that HRS possesses intrinsic immunostimulatory properties that may operate through the innate immune system.

Methods:

We immunized different strains of mice (C57BL/6, B6.G7, NOD.Idd3/5, DO11.10/Rag2-/-, and C3H/HeJ) with soluble HRS (Jo-1) or appropriate control proteins (maltose binding protein; MBP) via the intramuscular (IM) route. To evaluate the resulting immune response, we determined IgG anti-Jo-1 and anti-MBP antibody levels in the sera of mice immunized with different proteins using standard solid phase ELISA. As a measure of in vitro T cell proliferation, we CFSE labeled splenocytes or LN cells derived from these mice and then co-cultured cells with various antigens for 96 hours before flow cytometric assessment of CFSE dilution. Immunohistochemical staining of cell surface markers (CD3, CD4, CD8, CD44, CD11c, F4/80, B220, CCR5) permitted characterization of inflammatory infiltrates resulting from our IM immunization protocol. Quantification of antigen-induced muscle inflammation was based on a scoring system combining the relative intensity and distribution of lymphocytic infiltrates in multiple fields viewed under high power magnification, where 0=no inflammation, 1=minimal inflammation, 2=moderate inflammation, and 3=severe inflammation. Severity scores for muscle inflammation were compared using the Mann-Whitney U-test.

Results:

IM immunization with a murine HRS fusion protein induced significant muscle inflammation (relative to MBP control protein) in multiple congenic strains of C57BL/6 and NOD mice. Infiltrates occurred as early as 7 days post immunization and persisted as long as 7 weeks following a single administration of soluble HRS protein. Immunohistochemical staining indicated that these infiltrates were composed primarily of CD3+CD44+CCR5+ lymphocytes admixed with smaller numbers of B cells and macrophages. Corresponding to these histopathologic findings, ELISAs demonstrated class-switched antibody responses to HRS at each of these time points. Measurement of T cell responses to immunizing antigens through CFSE proliferation assays also revealed a level of antigen-specific priming. Parallel experiments in DO11.10/Rag2-/- (OVA-specific TCR transgene) and C3H/HeJ (TLR4-/-) mice showed that HRS could induce exuberant muscle inflammation in the absence of TCR or TLR4 signaling, further implicating alternative components of the innate immune response.

Conclusion:

Based on IM immunization with a soluble derivative of murine HRS, the reported experiments demonstrate that this putative autoantigen can trigger innate immune responses which bypass BCR and TCR signaling to generate significant muscle inflammation in a novel model of idiopathic inflammatory myopathy.

To cite this abstract, please use the following information:
Soejima, Makoto, Kang, Eun Ha, Katsumata, Yasuhiro, Gu, Xinyan, Clemens, Paula, Ascherman, Dana; The Role of Innate Immunity in a Model of HRS-Induced Myositis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :935
DOI: 10.1002/art.28703

Abstract Supplement

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