In vitro T-lymphocyte response and house dust mite-induced bronchoconstriction

Background: There is considerable evidence that T cells may play an important role in asthma. The purpose of this study was to determine whether the responsiveness of T lymphocytes to mite allergen stimulation in vitro is a determinant of bronchial response to house dust mite (HDM) allergen challenge in subjects who are allergic to HDM. Methods: Peripheral blood was taken from seven healthy nonatopic subjects and 23 subjects with positive skin test reactions to HDM. Of the subjects in the latter group, 16 had an asthmatic reaction on inhalation challenge with HDM extract (HDM-responders), whereas the remaining seven had a negative reaction (HDM allergic). The proportion of subsets of T lymphocytes and their activation and the amount of IL-2, IL-4, IL-5, and interferon-gamma released in the supernatants with and without stimulation with the HDM extract were determined. Results: Without stimulation, the proportions of subsets of T lymphocytes and their activation were similar between groups. When stimulated with the HDM allergen, the proportion of CD4(+)CD25(+) cells from HDM responders was significantly higher than those in the control group. Comparison within groups of cell cultures with and without stimulation with the mite allergen showed that the proportion of CD4(+), CD4(+)CD25(+), CD4(+)/CD8(+) and CD3(+)HLADR(+) cells were significantly increased in HDM responders with stimulation; there was a trend for CD4(+)CD25(+) cells to be increased in the HDM-allergic subjects; no increase in any T-lymphocyte subsets was found in the control subjects. The release of IL-5 was significantly greater in HDM responders than in the other two groups. The severity of the immediate asthmatic reaction was significantly associated with the degree of nonallergic bronchial hyperresponsiveness and the amount of IL-5 released but not with the level of specific IgE to the mite allergen or subsets of T lymphocytes with and without stimulation. Conclusion: The findings suggest that responsiveness of T lymphocytes to allergen challenge in vitro may play a role in determining the bronchial response to the allergen in vivo.