IN-VITRO T-LYMPHOCYTE RESPONSE AND HOUSE-DUST MITE-INDUCED BRONCHOCONSTRICTION

Background: There is considerable evidence that T cells may play an im portant role in asthma. The purpose of this study was to determine whe ther the responsiveness of T lymphocytes to mite allergen stimulation in vitro is a determinant of bronchial response to house dust mite (HD M) allergen challenge in subjects who are allergic to HDM. Methods: Pe ripheral 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 lymph ocytes and their activation and the amount of IL-2, IL-4, IL-5, and in terferon-gamma released in the supernatants with and without stimulati on 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 pr oportion of CD4(+)CD25(+) cells from HDM responders was significantly higher than those in the control group. Comparison within groups of ce ll 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 st imulation; there was a trend for CD4(+)CD25(+) cells to be increased i n the HDM-allergic subjects; no increase in any T-lymphocyte subsets w as found in the control subjects. The release of IL-5 was significantl y 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 amoun t 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. Con clusion: The findings suggest that responsiveness of T lymphocytes to allergen challenge in vitro may play a role in determining the bronchi al response to the allergen in vivo.