Excessive helper T-cell function in patients with idiopathic pulmonary fibrosis: correlation with disease activity.
Peripheral blood T lymphocytes from patients with idiopathic pulmonary fibrosis and matched normal controls were examined for their helper function in an in vitro antibody synthesis assay. This assay measures the dose-related T-cell regulation of antibody production by B cells in the presence of pokeweed mitogen. Eight patients of 14 expressed significantly increased helper T-cell activity, three exhibited no change, and three had depressed helper T-cell function. All of the patients with excessive helper T-cell function had an active neutrophilic alveolitis as determined by bronchoalveolar lavage on the day of study. Five of the 14 patients studied were determined to have a low percentage of neutrophils (less than 10%) in their BAL fluid. None of these were found to express excessive helper T-cell function; in fact three of the five had depressed helper T-cell function. No correlation between steroid therapy or smoking history and the expression of excessive helper function was observed. None of the peripheral blood T-cells from IPF patients were actively producing IL-2 in vitro without further stimulation, providing evidence against constitutive production in vivo. T cells were also examined for their ability to produce lymphokines promoting fibroblast proliferation. Enhanced stimulation of fibroblast proliferation was shown to positively correlate with disease activity as determined by the degree of neutrophilic alveolitis (r = 0.68). The significant correlation between neutrophilic alveolitis and excessive helper T-cell function observed here suggests that altered systemic immunoregulation accompanies local inflammation. The further participation of patient T cells in promoting fibroblast proliferation may contribute to the development of fibrosis, or to the contrary may be an attempt to limit the fibrotic process.