Correlation of house dust mite–specific lymphocyte proliferation with IL-5 production, eosinophilia, and the severity of symptoms in infants with atopic dermatitis

Abstract

Because house dust mite (HDM)–specific IgE antibody (IgE-RAST) is usually not detectable in infants with atopic dermatitis (AD), HDM has not been regarded as the cause of infantile AD. The level of HDM–specific lymphocyte proliferation (expressed as stimulation index measured by flow cytometry [SIF]), however, was found to be markedly elevated in AD infants. This suggests that the sensitization of T cells to HDM extract occurs even in infancy. Moreover, the level of HDM-SIF is correlated closely with the severity of infantile AD, suggesting that HDM is a major cause of this disease not only in adults and children but also in infants. Although the level of HDM-SIF did not correlate with the level of HDM-specific IgE-RAST in infants with AD, it did intimately correlate with the absolute number of peripheral blood eosinophils. Because T lymphocytes are known to secrete some cytokines, such as IL-5, that enhance the proliferation of eosinophils, we measured the IL-5 production by peripheral blood mononuclear cells in infants with AD on stimulation with HDM extract. The amount of IL-5 production is significantly higher in infants with AD, as well as in children with AD, than that found in nonatopic control subjects. Moreover, the level of IL-5 production is correlated closely with the level of HDM-SIF in infants with AD. Taken together, these results suggest that HDMs play an important role in the development of infantile AD by inducing IL-5 production from HDM-specific T lymphocytes. (J Allergy Clin Immunol 1998;101:84-9.)