PHENOTYPIC CHARACTERIZATION OF T-LYMPHOCYTES EMIGRATING INTO LUNG-TISSUE AND THE AIRWAY LUMEN AFTER ANTIGEN INHALATION IN SENSITIZED MICE

Cytokines released from CD4(+) T lymphocytes contribute to the pathoge nesis of asthma by influencing the differentiation and function of eos inophils, the primary effector cells that cause airway epithelial dama ge, Using a model of ovalbumin (OA)-induced, eosinophil-rich chronic l ung inflammation in sensitized mice, we have defined the role of T lym phocytes further by using three-color flow cytometry to characterize t he adhesion and activation antigens that may be associated with the mi gration of these cells into the lung and airway lumen. OA inhalation i n OA-sensitized C57BL/6 mice resulted in an early (6 to 24 h) influx o f neutrophils into the bronchial lumen as enumerated by bronchoalveola r lavage (BAL), which was followed by a marked accumulation of lymphoc ytes and eosinophils between 24 to 72 h. Phenotypic analysis of BAL or lung tissue T cells showed that most Thy-1(+) CD3(+) T cells were CD4 (+) (CD4:CD8 ratio of 3 to 4:1). The majority (90%) of the T cells in lung or BAL fluid expressed alpha beta T-cell receptors (TCR). Only 3 to 7% of the T cells were gamma delta TCR(+) even though almost 25% of the T cells were CD4(-) CD8(-). There were very few natural killer (N K) or B cells in BAL fluid compared with 15% B cells in dissagregated lung tissue, In contrast to T cells in spleen, almost all the lung and BAL T cells were of the memory phenotype, as ascertained by the expre ssion of high levels of CD44 and by the absence of L-selectin and CD45 RB on the cell surface. Fifty to ninety percent of lung and BAL T cell s from vehicle-sensitized or OA-sensitized and challenged mice express ed the adhesion molecules CD11a (LFA-1), CD54 (ICAM-1), and CD49d (VLA -4). The early T-cell activation marker CD69 was upregulated on 30% of the lung and BAL T cells in OA-sensitized mice after antigen inhalati on. When BAL fluid T cells from OA-sensitized and challenged mice were analyzed for their coexpression of adhesion and/or activation molecul es, 75% of the cells that expressed one of three adhesion molecules, C D54, CD49d, or CD11a, also expressed at least one of the other two ant igens. At least 15% of BAL T cells had all three of these molecules on their cell surfaces. The OA-dependent, temporally regulated emigratio n of T cells into the bronchial lumen after exposure to aerosolized an tigen may be correlated with the accumulation of cells that express th e memory phenotype with enhanced expression of adhesion molecules.