ALLERGIC RHINITIS TO RAGWEED POLLEN .2. MODULATION OF HISTAMINE-RELEASING FACTOR PRODUCTION BY SPECIFIC IMMUNOTHERAPY

A number of cytokines, including histamine-releasing factors (HRFs), have a role to play in IgE-mediated asthma. However, the influence of HRF in allergic rhinitis without asthma remains to be revealed. This article presents a double-blind, placebo-controlled study on the role of HRF in ragweed-allergic rhinitis and its modulation by natural pollen exposure and specific immunotherapy (IT). Twenty-seven patients allergic to ragweed were randomly assigned to receive either preseasonal alum-precipitated aqueous extracts of ragweed or placebo. Before the onset of therapy and during the ragweed-pollen season, subjects were evaluated for each of the following: clinical scores, ragweed IgE and IgG antibody levels, and spontaneous and allergen-driven HRF production. Thirteen nonatopic volunteers were also studied in the same protocol. First, before the initiation of therapy, more HRF was produced by both unstimulated and ragweed-stimulated mononuclear cells (MNCs) of atopic subjects as compared to MNCs of nonatopic subjects. Second, MNCs of the placebo-treated group produced significantly more spontaneous and ragweed-specific HRF during the pollen season compared to the preseasonal values. Finally, specific IT not only improved the clinical manifestation of allergy but also prevented the seasonal rise of spontaneous and ragweed-driven HRF production, along with a well-known change in other immunologic parameters associated with successful IT.