IDENTIFICATION OF IGE-BEARING CELLS IN THE LATE-PHASE RESPONSE TO ANTIGEN IN THE LUNG AS BASOPHILS

We have carried out studies to ascertain whether the histamine-contain ing, IgE-bearing cells found in the bronchoalveolar lavage (BAL) fluid obtained during the late-phase response following subsegmental antige n challenge of human airways are predominantly basophils or mast cells . Four lines of evidence suggest that most are basophils: (1) The cell s fulfill morphologic criteria for light microscopy. (2) Cell surface markers determined by immunofluorescence and flow cytometry revealed t hat the IgE-bearing cells express the leukocyte antigens Fc gamma RII and the beta 2 integrins, LFA-1 and Mac-1, but do not express the mast cell-associated c-kit receptor for stem cell factor. (3) The late-pha se histamine-containing cells in late-phase BAL fluids have the functi onal characteristics of basophils in their secretory responses to anti -IgE, the f-met peptide, and phorbol ester TPA. (4) The cells have a f unctional histamine type 2 receptor, a characteristic of basophils, no t mast cells. We conclude that basophils infiltrate the lower airways hours after antigen exposure. These cells may be responsible for the m ediator release observed at that time.