Quantification of immunoglobulins in respiratory tract secretions of the horse

Abstract

Lavage techniques were used to obtain secretions from the nasal cavity, trachea and bronchi of conscious horses. The techniques, which utilised fibreoptic endoscopy for recovery of tracheal and bronchial secretions, were well tolerated by the horses. The recovery rates of the lavaged fluids were acceptable, but were lowest for bronchial secretions, and there was minimal contamination by blood. The fluids were analysed for IgG and IgM by single radial immunodiffusion, and for IgA and albumin by rocket immunoelectrophoresis. Relative to albumin there was significantly more IgA and IgM, and significantly less IgG, in the nasal cavity than the trachea. IgA and IgM levels were greatest in the nasal cavity and decreased progressively to the bronchi, whereas IgG levels showed the reverse trend. The immunoglobulin: albumin ratios of secretions taken from many levels of the tract were significantly higher than those of serum, suggesting local production of immunoglobulin in the respiratory tract.