Reduced tracheal mast cell numbers in adjuvant-sensitized rats associated with reduced pulmonary reactivity

PVG/c inbred rats were sensitized by intra-peritoneal injection of DNP 19-ovalbumin with or without heat-killed Bordetella pertussis as adjuvant. The use of adjuvant was associated with a greater serum IgE, greater cutaneous immediate hypersensitivity, but no increase in immediate pulmonary reactivity to aerosol challenge. The number of mast cells in the trachea of adjuvant-sensitized rats was significantly reduced when compared with both unsensitized and allergen sensitized rats but this reduction in mast cell number did not occur in the skin. The reduction in tracheal and possibly other airway mast cells may explain the failure of the adjuvant sensitized rats to show increased pulmonary reactivity despite the increased serum IgE. The B. pertussis may have acted on the mediastinal lymph nodes, which drain both the peritoneal cavity and the lungs, to produce the observed reduction in tracheal mast cells.