The balance between lung regulatory T cells and Th17 cells is a risk indicator for the acute exacerbation of interstitial lung disease after surgery: a case-control study

BACKGROUND: Acute exacerbation (AE) of interstitial lung disease (ILD) (AE-ILD) is a life-threatening condition and the leading cause of 30-day mortality among patients who underwent pulmonary resection for lung cancer in Japan. This study was conducted to clarify the characteristics of the immune environment of lung tissues before the onset of AE-ILD. METHODS: This retrospective matched case-control study compared the immune phenotypes of helper T cells in lung tissues from patients with and without AE-ILD after surgery. In total, 135 patients who underwent surgical resection for lung cancer and were pathologically diagnosed with idiopathic interstitial pneumonia (IIP) at our institute between 2009 and 2018 were enrolled. Thirteen patients with AE-IIP and 122 patients without AE (non-AE) were matched using a propensity score analysis, and 12 cases in each group were compared. We evaluated the percentages of T helper (Th)1, Th2, Th17, regulatory T (Treg), and CD8 cells in CD3(+) T cells and the Th1:Th2, Th17:Treg, and CD8:Treg ratios in patients with AE by immunostaining of lung tissues in the non-tumor area. RESULTS: We found a significant difference in the lung Th17:Treg ratio between the AE and non-AE groups (1.47 and 0.79, p = 0.041). However, we detected no significant differences in the percentages of lung Th1 (21.3% and 29.0%), Th2 (34.2% and 42.7%), Th17 (22.3% and 21.6%), Treg (19.6% and 29.1%), and CD8(+) T cells (47.2% and 42.2%) of CD3(+) T cells between the AE and non-AE groups. CONCLUSION: The ratio of Th17:Treg cells in lung tissues was higher in participants in the AE group than in those in the non-AE group. CLINICAL TRIAL REGISTRATION: This study was approved by the ethics committee of our institute (2,016,095). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12890-023-02362-2.