B and T cells in lung tissue are associated with smoking and forced vital capacity in idiopathic pulmonary fibrosis and familial pulmonary fibrosis.

BACKGROUND: The exact pathogenesis of idiopathic pulmonary fibrosis (IPF) is unknown, but B and T cells, as part of the adaptive immune system, may play a role. Our aim was to immunohistochemically characterize B and T cells in fibrotic lung tissue and to study whether clinical features were associated with the numbers of cells. METHODS: We characterized immunohistochemically the expression of CD20 (a B-cell marker) and CD3 (a T-cell marker) in cells from surgical lung biopsies of patients with IPF (N = 34) and familial pulmonary fibrosis (FPF, N = 16), as well as in noncancerous control tissues from patients who had undergone lung cancer surgery (N = 11). RESULTS: CD20 was expressed in lymphoid cells occurring in aggregates often located near fibroblast foci. In contrast, CD3 expressions was observed in groups of cells and as scattered single cells. The expression of CD20 was higher in patients with IPF than in those with FPF or in the controls. CD3 expression was higher in the patients with IPF and FPF than in the controls. CD20 and CD3 expressions were lower in smokers than in non-smokers or ex-smokers. Higher CD20 expression was associated with a higher forced vital capacity (FVC) in patients with IPF, whereas a high number of T cells was associated with lower FVC in patients with FPF. CONCLUSIONS: Differences were evident between FPF and IPF regarding the expressions of CD20 and CD3. The associations of B and T cells with smoking and lung function are novel observations that merit further investigation.