Tripartite motif containing 21 autoimmunity primes CD8+ cell-mediated lung inflammation: an in vivo model of interstitial lung disease pathogenesis.

Background: Anti-Ro52 [Tripartite Motif Containing 21 (TRIM21)] antibodies are strongly associated with interstitial lung disease (ILD) in connective tissue diseases (CTDs), yet the underlying mechanisms remain elusive. This study aimed to elucidate the mechanisms by which TRIM21 autoimmunity drives ILD using an in vivo model.

Methods: A murine model of TRIM21 autoimmunity was established by immunizing mice with full-length recombinant TRIM21 protein. Lung immune infiltration and antibody production were assessed. To mimic viral triggers, mice received poly(I:C). Immune cell subsets and transcriptional changes were analyzed using flow cytometry, RNA sequencing, and immunohistochemistry.

Results: TRIM21 immunization induced systemic autoantibody production and B cell activation, which were associated with selective pulmonary inflammation marked by IgG deposition. Upon poly(I:C) challenge, lung inflammation was markedly exacerbated, with increased infiltration of CD8⁺ cells and CD11b⁺ myeloid cells and enrichment of chemokine signaling pathways. RNA sequencing identified Ccl6 as a top upregulated gene, and its protein expression was spatially validated in inflamed lung tissue.

Conclusion: These findings support a pathogenic role for anti-Ro52/TRIM21 autoimmunity in CTD-associated ILD. Our in vivo model reveals a lung-predominant inflammatory response associated with CD8⁺ cell that is amplified by viral mimicry and accompanied by CCL6 signaling, offering mechanistic insight and potential therapeutic targets in anti-Ro52 positive ILD.