IL-13-producing BLT1-positive CD8 cells are increased in asthma and are associated with airway obstruction.

BACKGROUND: The role of CD8 T lymphocytes in the pathogenesis of asthma is not well understood. We investigated whether a subset of IL-13-producing BLT1-positive CD8 T lymphocytes are present in asthmatic airways and are associated with impaired lung function.
METHODS: Bronchoalveolar lavage (BAL) cells were obtained from asthmatic (n = 39) and healthy control (n = 28) subjects. Cells were stimulated with phorbol ester and ionomycin in the presence of brefeldin A and stained for CD8, BLT1, and intracellular IL-13. The frequency of IL-13-producing BLT1-positive CD8 T lymphocytes was compared between the two groups and related to lung function, serum IgE levels, and reticular basement membrane (RBM) thickness.
RESULTS: A subset of CD8 T lymphocytes expressing BLT1 and producing IL-13 were detected in the airways of all asthmatic subjects. The frequency of this subset among recovered lymphocytes was significantly higher in the airways of asthmatic subjects compared with controls (mean ± SEM: 16.2 ± 1.4 vs 5.3 ± 0.5, respectively, P < 0.001) and correlated positively with serum IgE levels and RBM thickness. More importantly, the frequency of CD8 T lymphocytes co-expressing BLT1 and IL-13 was inversely related to FEV1 and FEF[25-75] percent predicted values (P < 0.001).
CONCLUSIONS: A subset of CD8 T lymphocytes expressing BLT1 and producing IL-13 is present in the airways of asthmatics. The accumulation of these cells is associated with airway obstruction, suggesting that they may play a significant pathogenic role in bronchial asthma.