Activation of Lymphocytes in the Pulmonary Inflammatory Response to Silica

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Abstract
Lymphocytes were separated from the parenchymal lung tissue of mice administered either silica or titanium dioxide particles by intratracheal injection. There was an approximately 10-fold increase in the number of T-lymphocytes recovered from silica-treated animals at 2 weeks after injection. This was accompanied by an increase in the percentage of separated cells expressing the interleukin-2 receptor and by enhanced spontaneous DNA synthesis in serum-free culture. No such changes were demonstrable in cells obtained from animals administered titanium dioxide. These results confirm that an influx of T-lymphocytes occurs as part of the early pulmonary inflammatory response to silica particles. Furthermore, lymphocytes in the lung are functionally activated by at least two criteria. Activated T-lymphocytes may play a role in the induction of fibroblast proliferation and collagen synthesis that occurs in silicotic lung disease.