Seasonal increase of spontaneous histamine release in washed leucocytes from rhinitis patients sensitive to grass pollen

The spontaneous histamine release (SHR) in basophils from patients sensitive to grass pollen has been studied before and during the 1987 grass pollen season. Nineteen patients were recruited on seasonal rhinitis symptoms, positivity for cutaneous tests and for serum-specific IgE with grass pollen. At the time of the biological investigations the patients were following a clinical trial of hyposensitization, including placebo, calcium phosphate and aluminium hydroxide-adsorbed grass pollen extract treatments. During the pollen season, grass pollen counts and clinical scores were checked over a 40-day period. Mean SHR was significantly higher during the pollen period than before, for the whole population of 19 patients (10.9% and 4.6%; P< 0.005) as well as when the high SHR responders were-excluded (5.5% and 3.6%; P< 0.01). No significant correlation existed between SHR and clinical scores or treatments. SHR could be inhibited at 4°C, in absence of Ca⁺⁺ or of oxidative metabolism and thus originated from cells actively secreting histamine.