**8. Conclusions**

Despite increased recognition of CTD-associated ILD and its prognostic significance, the pathologic mechanisms that lead to the considerable pulmonary changes are not yet fully defined, and thus, the only limited progress has been so far made in the therapeutic domains. Immunosuppression therapy remains the mainstay of treatment for CTD-ILD. To generate significant advances in therapeutic intervention strategy, fundamental understanding of the pathogenesis of CTD-ILD is essential. As noted, we had an opportunity to carefully study the cases of early-stage IP associated with PM by utilizing lung biopsy tissue and PBLs. The T cell receptor (TCR) repertoire study combined with histological analysis demonstrated substantial CD3+ T cell lung infiltrates with specific oligoclonal TCR usage that differed from those in PBL, suggesting a pivotal role for T cells in the pathogenesis of PM-associated IP via antigen-driven immune responses. The results imply potential elucidation of specific antigen(s) that oligoclonal, lung-infiltrating T cells recognize, which may provide novel insights into the development of immunospecific treatments such as molecular-targeted or specific T cell-targeted therapeutics.

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