EXPRESSION OF ACTIVATION MARKERS BY HUMAN LUNG T-CELLS AFTER ADHERENCE TO LUNG EPITHELIAL-CELLS

Both increased T cell numbers and their increased activation state hav e implicated an important role for T cells in chronic inflammatory rea ctions seen in the airways of (allergic) asthmatics. Airway epithelial cells are frequently exposed to stimuli that cause the release of med iators and the expression of cell adhesion molecules. We have examined whether human airway epithelial cells can activate lung-derived T cel ls. Clonal lung T cells showed an increased adherence to transformed a irway epithelial cells that had been exposed previously for 2 h to hum an recombinant interferon-gamma (IFN-gamma; 100 U/ml). After an additi onal 16-24 h of culturing in the absence or presence of epithelial cel ls, T cells expressed increased levels of both the alpha-chain of the interleukin-2 receptor (IL-2R, CD25) and the transferrin receptor (CD7 1), both markers of T cell activation. T cells apparently activated by epithelial cells, however, did not produce IFN-gamma or IL-4 nor show ed an increased proliferation on the addition of IL-2 (5-50 U/ml). The induced adherence to and the activation of T cells by epithelial cell s is mediated largely by CD2 and its ligand lymphocyte functional anti gen-3, a pathway known to up- and downregulate T cell functions.