Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology
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Occupational asthma due to Western Red Cedar (WRCA) is attributed to sensitization to plicatic acid (PA), but does not appear to be dependent on PA-specific IgE antibodies. Exposure to PA induces histamine release in vivo and in vitro, so if IgE is not important, other mechanisms of histamine release must presumably operate in WRCA. To explore the possible role of histamine-releasing factors in WRCA, peripheral blood mononuclear cells were obtained and cultured with PA, PA-albumin conjugate plicatic acid-human serum albumin (PA-HSA), grass pollen or Concanavalin A using a standard histamine releasing factor (HRF) generation protocol. ⋯ Both PA and PA-HSA induced the production of small amounts of HRF by PBMC of WRCA patients, but a similar degree of HRF generation was also observed in PBMC from the atopic asthmatic, atopic nonasthmatic, and non-atopic subjects. In contrast, grass pollen induced the production of HRF by PBMC from the subjects with positive skin tests to grass pollen but not by PBMC of non-atopic subjects, confirming that our methods and assay were capable of detecting antigen-specific HRF production. Since neither PA nor PA-HSA induced significantly elevated HRF production from PBMC of WRCA patients, it seems unlikely that PA-induced HRFs play a substantial role in the pathogenesis of WRCA.