Detection of house dust mite (HDM)-specific IgE antibodies on nasal mast cells from asthmatic patients whose skin prick test and RAST are negative for HDM.

Mast cells are found in nasal smears of pediatric patients with perennial bronchial asthma whose skin prick test and radioallergosorbent test (RAST) are negative for inhalant allergens. IgE antibodies were demonstrated on these mast cells by monoclonal anti-human IgE antibodies, whereas IgG antibodies were not detected by monoclonal anti-IgG antibodies. In order to pursue the causative allergen for asthma in these patients, binding potential between IgE antibodies on nasal mast cells and house dust mite (HDM), the most prevalent aeroallergen, was examined by an immunochemical technique. Out of 9 patients whose skin prick test and RAST were negative for HDM, 7 were found to have HDM-specific IgE antibodies on their nasal smear mast cells. None of these 7 patients had IgE antibodies to cedar pollen, a negative control aero-allergen, on their mast cells. Specific binding of HDM on the mast cells was further confirmed by the fact that nasal mast cells from patients with egg allergy bound egg white but not HDM on their surface. Preincubation of mast cells with anti-IgE antibodies inhibited binding of HDM on the mast cells, indicating that HDM was bound to surface IgE antibodies on the mast cells. These experiments enabled us to expeditiously identify sensitization to an inhalant allergen, such as HDM, in young asthmatic patients whose allergen cannot be found by conventional laboratory diagnostic procedures.