The effect of preseasonal immunotherapy on the production of histamine-releasing factor (HRF) by mononuclear cells from patients with seasonal asthma: results of a double-blind, placebo-controlled, randomized study.

The effect of immunotherapy on the production of histamine-releasing factor (HRF) by mononuclear cells (MNC) from patients with seasonal asthma was investigated in a double-blind, placebo-controlled, randomized study. Twenty-four patients with asthma were randomly divided into a placebo-treated group and a grass pollen-treated group. In vitro production of HRF by MNCs and the provocative concentration of histamine that causes 20% fall in FEV1 were measured before and after immunotherapy, and symptoms were monitored during the pollen season. MNCs from the patients were either cultured alone, spontaneous HRF production (spHRF), or in the presence of grass allergens (grass-stimulated HRF production), and the supernatants were assayed for HRF activity with basophils from a single donor after the study. We found that MNCs from patients with seasonal asthma to grass pollen spontaneously produce substantial amounts of HRF. The group of patients treated with placebo developed typical symptoms in the pollen season and also an increase in HRF production. In contrast, patients treated with grass pollen demonstrated reduced symptoms and no increase in spHRF production. A high degree of correlation between spHRF productions and symptom scores in both treated groups was noted. After 2 years of immunotherapy, allergen-stimulated HRF production decreased significantly, whereas spHRF production decreased significantly only in the patients who were clinically benefitted. The change in the provocative concentration of histamine that causes 20% fall in FEV1 during the pollen season highly correlated with the change in HRF production. The results of this study suggest that HRF might be involved in the pathogenesis of atopic asthma.