Changes in T-lymphocyte subpopulations after antigenic bronchial provocation in asthmatics.

To determine whether inhaled agents can alter T-cell subsets in the peripheral blood of patients with bronchial asthma, we tested six asymptomatic asthmatics who were sensitive to mixed grass (positive skin test) with mixed grass extract, methacholine, and an antigen to which they were not sensitized (negative skin test). Levels of OKT4 cells (helper T lymphocytes) were reduced in the peripheral blood immediately after the challenge with mixed grass extract, and remained low for at least 72 hours. Levels of Ia-positive (activated) T cells were increased 48 hours after the challenge. No changes were observed in any of these T-cell subpopulations after challenge with methacholine or after the inhalation of an equal amount of an antigen to which the subjects were not sensitized. These results suggest that the selective loss of circulating helper T cells and an increase in activated T cells after an asthmatic attack induced by antigenic inhalation may serve as an indicator of immune-mediated bronchoconstriction.