HUMAN AIRWAY EPITHELIAL-CELLS STIMULATE T-LYMPHOCYTE LCK AND FYN TYROSINE KINASE

Previous studies have shown that human airway epithelial cells (AEC) c an stimulate allogeneic peripheral blood T-lymphocyte (PET) proliferat ion. We now sought to determine which AEC surface molecule/T-cell core ceptors are involved in this process. AEC-induced PET proliferation wa s inhibited by 25 mu M genestein or herbamycin A (0.9 and 1.8 mu M), b oth tyrosine kinase inhibitors, Anti-phosphotyrosine immunoblots perfo rmed on PET lysates after coculture with AEC demonstrated phosphorylat ion of 56kD and 60kD bands. To determine whether CD3 associated p59fyn , or CD4 and CD8 associated p56lck phosphotyrosine kinases (PTK) were involved, we assayed kinase activity in lymphocyte lysates immunopreci pitated with anti-p56lck and p59fyn mAbs. PET cells or murine T-cell l ine transfectants expressing human CD4 (3G4) or human CD8 alpha (3G8) were cocultured with AEC or A549, an alveolar-like cell line lacking c lass II Ag expression. After A549 or AEC coculture, p56lck activity in PB T-cells peaked at 2 min whereas p59fyn kinase activity continued t o rise at 8 min. AEC (expressing class II Ags) stimulate PTK activity in both 3G8 and 3G4 cells. A549 stimulated p56lck in 3G8, but not in 3 G4 cells. This activation of p56lck was not blocked by preincubation o f A549 with anti-class I or anti-CD id mAbs. An antibody generated in our laboratory, which recognizes an epithelial specific surface molecu le (mAb L12) and which blocks AEC driven PET proliferation, was shown to block PTK activity of peripheral blood T-cell lysates, though not o f 3G8 lysates. These studies suggest that AEC are capable of stimulati ng CD4 and CD8 associated lck and CD3 associated fyn kinases through c lass II dependent and independent pathways.