Bronchoalveolar lavage fluid and blood natural killer and natural killer T‐like cells in cryptogenic organizing pneumonia

Abstract Background and objective Natural killer ( NK ) cells appear to be involved in the development of interstitial lung diseases ( ILD ). The purpose of this study was to investigate the involvement of NK and natural killer T ( NKT )‐like cells in two recognized cytotoxic ILD with systemic character, hypersensitivity pneumonitis ( HP ) and cryptogenic organizing pneumonia ( COP ), compared with idiopathic pulmonary fibrosis ( IPF ) and controls. Methods B ronchoalveolar lavage fluid ( BALF ) and peripheral blood ( PBL ) cells and lymphocyte subsets of 83 patients (26 with COP , 19 with HP and 38 with IPF ) and 10 controls were prospectively studied by flow cytometry. Results The percentage of NK and NKT ‐like cells was lower in BALF than in PBL in all patient groups and controls. Patients with COP presented with statistically significantly higher NK and NKT ‐like cell counts in BALF compared with controls ( P = 0.044 and P = 0.05 respectively) and IPF ( P = 0.049 and P = 0.045 respectively). BALF NKT ‐like cell count correlated with PBL NKT ‐like cell count only in COP (r = 0.627, P = 0.002). In addition, a significant positive correlation between BALF NKT ‐like cell and PBL cytotoxic T CD 8+ cell count was observed in COP (r = 0.562, P = 0.006) but not in HP , IPF or controls. Conclusions Our study provides for the first time evidence for the implication of NKT ‐like cells in the pathogenesis of COP , as part of both localized and systemic cytotoxicity.