The effect of immunotherapy on humoral and cellular responses in ragweed hayfever

The effect of specific immunotherapy on several in vitro responses to ragweed antigen E has been evaluated in 17 atopic patients with ragweed hayfever. The methods employed were leukocyte histamine release, measurement of specific IgE anti-ragweed antibody and specific IgG anti-ragweed antibody, lymphocyte proliferation, and the production of two lymphocyte mediators (migration inhibitory factor and mitogenic factor). The duration of treatment and symptom improvement were also recorded for comparison. Immunotherapy was associated with a decrease in leukocyte sensitivity for histamine release to ragweed antigen E in a majority of the patients. In addition, there was a significant decrease in IgE anti-ragweed antibody and a significant increase in IgG anti-ragweed antibody. Immunotherapy also resulted in a significant decrease in lymphocyte responsiveness to ragweed antigen E as measured by proliferation and the production of mediators. Symptomatic improvement was best correlated with the presence of IgG anti-ragweed antibody responses. The production of this antibody was also associated with a decrease in lymphocyte responsiveness. The results of this study indicate that specific immunotherapy in ragweed-sensitive patients induces alterations in immunologic reactivity to ragweed antigen in vitro. This response is antigen specific, includes elements of both humoral and cellular immunity, and may account for the clinical improvement that is often observed in patients who undergo this form of therapy.