Depletion of circulating allergen-specific T-H2 T lymphocytes after allergen exposure in asthma

Background: In allergic asthma, CD4(+) T lymphocytes are a fundamental component of local chronic inflammation. Their cytokine profile is oriented toward a T-H2 phenotype, characterized bg production of IL-4, IL-5, IL-10, and IL-13, Egress of T cells from blood to airways after allergen challenge has been described. Objective: We have studied a cohort of six patients with asthma who had multiple allergies to investigate how exposure to allergen afferts the proliferation of peripheral CD4(+) T lymphocytes with different allergen specificities and lymphokine profiles. Methods: For each patient, CD4(+) T cell lines were generated by in vitro stimulation with sensitizing and with nonsensitizing allergens, and IL-4 and interferon-gamma production by these lines was assessed. Proliferation of peripheral blood CD4(+) T lymphocytes in response to the same allergens was measured before and 24 hours after inhalation challenge with a sensitizing allergen. Results: We found that each single sensitizing allergen can deplete peripheral blood of T-H2-type CD4+ T lymphocytes specific for all sensitizing allergens, but not of T-H1-type CD4(+) T lymphocytes. Conclusions: Our results suggest the existence of mechanisms capable of sorting disease-associated antigen specificities together with defined lymphokine patterns into T lymphocytes that can migrate to target organs, in allergic asthma.