Intraindividual reproducibility of nasal allergic responses to diesel exhaust particles indicates a susceptible phenotype

Previous research indicates that diesel exhaust particles (DEP) can augment allergen- driven allergic responses. In vivo nasal challenge offers a practical method to characterize variation in response to pulmonary toxicants and immunogens. We investigated the reproducibility of responses to determine whether susceptibility to DEPʹs adjuvant effects is intrinsic or extrinsic. Eighteen nonsmoking rhinitic volunteers with positive skin tests to ragweed were randomly assigned to allergen/placebo or allergen + DEP nasal challenge; after 30 days, the other “arm” was completed. We replicated the procedure 30 days later. Nasal washes were performed after challenge, and allergen-specific IgE and cytokines were measured by ELISA. Repeated challenge with allergen+DEP, but not allergen/placebo, produced reproducible responses for IgE, IL-4, and INF-γ. DEPs ability to enhance allergic responses was highly reproducible within individuals and was independent from response to allergen, suggesting that susceptibility to DEPs adjuvant effects is an intrinsic trait that can be quantified using combined allergen + DEP challenges.