RATIONALE: Progressive pulmonary fibrosis (PPF) can occur in the context of many of fibrotic interstitial lung diseases (f-ILD). In later phases, common immune mechanisms that lead to self-perpetuating fibrosis might play a role.

OBJECTIVE: We investigated if the peripheral blood immunological profile may differ in PPF patients from non-progressive f-ILD (non-PPF), as well as in relation to their clinical severity.

METHODS: Flow cytometric staining was performed on whole blood from 33 patients with f-ILD at diagnosis (11 PPF, and 22 non-PPF patients). All patients were treated following international guidelines and followed up one year when they were categorized as stable or progressors based on worsening respiratory symptoms, radiological evidence of disease progression, and/or decline of either forced vital capacity (FVC) or predicted carbon monoxide diffusing capacity (DLCO). Baseline immune populations were compared across groups.

RESULTS: In the f-ILD cohort we found: 1) a significant negative correlation between baseline FVC and CD8+HLA-DR+T cells, and central memory CD4+T cells; 2) a significant negative correlation between both baseline FVC and DLCO and the percentage of T helper type 1 (Th1) cells and CD4+CD28-HLA-DR+T cells. Compared to non-PPF, patients with PPF showed: 1) higher percentage of NK-T like cells; 2) a significant negative correlation between baseline FVC and the percentage of CD8 T cells.

CONCLUSION: the peripheral blood immunologic profiling of patients with f-ILD present common abnormalities, with an aged blood immune profile that is mainly associated with impaired lung function. Moreover, there is an increased cytotoxic immune response in PPF patients.