Allergic rhinitis to ragweed pollen. I. Reassessment of the effects of immunotherapy on cellular and humoral responses.

This work presents a double-blind, placebo-controlled study of 27 patients with allergic rhinitis to ragweed who received preseasonal desensitization immunotherapy [IT] with alum-precipitated aqueous ragweed extracts. We reassessed the following parameters in relation to clinical responses: clinical scores, nasal reactivity to a provocative dose of ragweed causing a 75% fall in airflow rate (PD75), ragweed IgE and IgG, and ragweed-induced basophil histamine release (BHR). First, the nasal PD75 correlated with the severity of nasal symptoms (p less than 0.05). Second, we confirmed a significant symptomatic improvement in the IT-treated group either by clinical scores (p less than 0.05) or the prevention of the seasonal fall of the PD75 (p less than 0.005). Also, IT reduced the seasonal rise of IgE (p less than 0.02) and induced an increase in IgG (p less than 0.01) and a decrease in BHR (p less than 0.03). There was a significant correlation between IgE and BHR (r = 0.80; p less than 0.01). After selecting out the effects of IgE, the BHR was still higher in the placebo-treated group than in the IT-treated group (p less than 0.02), suggesting the involvement of other modulating factors. Symptomatic improvement after IT correlated only with the summation of both IgE and BHR (PD75; r = 0.64; p less than 0.005). This observation suggests that the severity of clinical symptoms is determined by several interacting factors and not by the antibody response alone.