Background/Purpose: Polymyositis (PM) and dermatomyositis (DM) are systemic inflammatory myopathies. They sometimes accompany interstitial lung disease (ILD), which can lead often to fatal outcome. For PM and DM treatment, high dose corticosteroid and cytotoxic drugs are used as first line therapies. Additionally, the effectiveness of T- and B-cell targeted therapies for refractory PM/DM has been reported. Although the clinical evidence indicates the T- and B-cell involvement in the pathogenesis of PM/DM, the lymphocyte subsets that contribute to the pathogenesis remain unclear. Analyzing peripheral blood mononuclear cell (PBMC) subsets will provide important insights into the understanding of the immune status and the pathogenesis in PM/DM. The aim of this study was to elucidate the lymphocyte subset biases of peripheral blood from the patients with PM/DM.

Methods: PBMCs from 17 (4 PM and 13 DM) patients including 8 patients with ILDs and from 18 healthy donors (HDs) were examined for lymphocyte subsets with flow cytometry according to the standardized immunophenotyping (Nat Rev Immunol 2012;12:191-200). Lymphocyte subsets were compared among patients with ILDs, those without ILDs, and HDs. In 6 DM patients, the lymphocyte subsets before and after the successful treatment were compared.

Results: The PM/DM patients had larger subsets of naïve CD4 T and naïve B cells, and smaller subsets of naïve CD8 T, central memory CD8 T (CD8 T_CM), effector memory CD4 T (CD4 T_EM), Th1, and memory B cells than HDs. These biased subsets were compared among the patients with ILDs, those without ILDs, and HDs. The patients with ILDs had larger biases in all of these subsets, except for Th1 cell subset, than HDs. Similar trends were also observed in PM/DM patients without ILDs although the differences were not statistically significant. Among the biased subsets in the patients, the naïve B cell subset decreased and the memory B cell subset increased after treatment.

Conclusion: The biases in naïve and memory T- and B- cell subsets suggest abnormal homeostatic regulation or migration of the smaller subsets from the peripheral blood into the inflamed tissues in PM/DM. Normalization of the biases in B-cell subsets after treatment implies B-cell involvement in the pathogenesis. The biases in T- and B-cell subsets in the patients with ILDs may represent intensive autoimmunity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/abnormal-composition-of-circulating-t-and-b-cells-in-patients-with-polymyositis-and-dermatomyositis-is-more-biased-in-those-with-interstitial-lung-diseases/