Comparison of the in‐vivo and in‐vitro response to ragweed immunotherapy in children and adults with ragweed‐induced rhinitis

In order to compare results of allergen immunotherapy in paediatric and adult populations, 22 children with a history of ragweed hay fever were matched with an equal number of adults for skin sensitivity to ragweed and all were given a 1‐year course of immunotherapy with a partially purified ragweed extract. Biological responses were measured by nasal challenges with ragweed before therapy was started, after 12 weekly injections and when the maintenance dose had been reached and also by methacholine bronchoprovocation tests before and after 12 months of therapy. Skin‐test sensitivity to ragweed and control allergens, and ragweed‐specific IgE and IgG antibody responses were measured at the same intervals as the challenges and at the end of the study. The effect of the therapy on clinical symptoms was not evaluated. Before therapy the groups of adults and children were comparable by all indices, except for TAME esterase activity in nasal washes during ragweed nasal challenge which was significantly lower in children. During treatment, mediators released during sequential nasal challenges declined to undetectable levels in most patients and changes in nasal ragweed sensitivity were comparable in both groups. Ragweed IgE increases after 12 weeks of therapy and IgG levels at maintenance therapy tended to be higher in the children, but neither difference was statistically significant. At the end of the study IgE and IgG antibody levels were comparable in both groups. Results of methacholine inhalation tests did not change significantly in either group. The decrease in skin sensitivity to ragweed was similar in both groups. We conclude that ragweed immunotherapy leads to immunological and biological consequences that are comparable in children and adults.