Effect of allergen challenge on the percentage of natural killer T cells in patients with atopic asthma

Background: Invariant natural killer T (iNKT) cells produce cytokines that can influence the immune response to infection or allergen. Controversy surrounds their role in exacerbations of human atopic asthma. Objectives: To determine the effect of allergen challenge on iNKT cells' mobilization to the airways and blood and to establish the relationship between airway iNKT cells and bronchial sensitivity to methacholine and allergen in patients with atopic asthma. Methods: We performed flow cytometry analysis for the iNKT cell receptor V alpha 24 and V beta 11 on bronchoalveolar lavage (BAL) cells at baseline and 24 hours after segmental antigen challenge (SAC) (n = 8) and on peripheral blood mononuclear cells (PBMCs) at baseline and 6 to 7 hours after inhaled allergen (n = 10). Challenges were performed using standardized protein allergens to which the participants were sensitive. Results: The number of BAL eosinophils increased 24 hours after SAC. The low mean (SEM) baseline percentage of iNKT cells in the population of BAL CD4(+) T cells remained unchanged 24 hours after SAC (0.035% [0.01%] vs 0.049% [0.02%]; n = 8; P = .50). Likewise, the mean (SEM) percentage of iNKT cells in PBMCs was unchanged after inhaled allergen provocation (0.068% [0.033%] vs 0.057% [0.026%]; n = 1 0; P = .10). No correlation was found between iNKT cells in BAL and the sensitivity to inhaled methacholine or allergen. Conclusions: The percentages of both BAL and peripheral blood iNKT cells did not increase during allergen provoked asthmatic responses. Determination of iNKT cells in airway biopsy specimens would allow conclusively ruling against mobilization of iNKT cells in allergen-induced asthma exacerbation in humans. Ann Allergy Asthma Immunol. 2009;102:432-437.