Leukotriene C4 release in upper respiratory mucosa during natural exposure to ragweed in ragweed-sensitive children.

With high-pressure liquid chromatography and specific radioimmunoassay, the concentration of leukotriene C4 (LTC4) was measured in nasopharyngeal secretions (NPS) of groups of children with allergic rhinitis before, during, and after the ragweed-pollen season. Increase LTC4 concentrations in NPS were noted in all the children during the pollen season; the concentration of LTC4 increased from a preseasoned mean of 1.87 +/- 0.43 ng/ml to 5.52 +/- 0.7 ng/ml at the peak of the ragweed season (p less than 0.001). The mean LTC4 concentration 2 weeks after the end of the ragweed season declined only to about 4.45 +/- 1.04 ng/ml. The seasonal variation of LTC4 concentrations and symptom scores of the children paralleled the pattern of the ragweed-pollen count. All children studied were ragweed sensitive, and six children were additionally sensitive to Alternaria (mold). The mold-sensitive children demonstrated higher concentrations of LTC4 in their NPS before and continued to have high LTC4 levels after the peak ragweed season, coinciding with peaks of mold-spore counts. Data presented in this study suggest that mast cells and other target cells in the nasal mucosa of children with allergic rhinitis produce pharmacologically active mediators, such as LTC4, during natural exposure to ragweed or Alternaria.