ABSTRACT
The normal respiratory tract immune system has recently undergone extensive characterization in the dog and some similar studies have been conducted in the cat. The innate immune system (mucociliary clearance and phagocytic cells) is of particular significance in the respiratory tract (440), and relatively high doses of antigen are required to overwhelm these defences and ensure translocation to local lymph nodes for generation of an immune response. The dog has been used as an experimental model for studies of the pulmonary immune response, and instillation of antigens into specific lung lobes is able to generate populations of antigen-specific B lymphocytes that recirculate to sites of antigen deposition, leading to production of specific antibody of the IgG, IgM and IgA classes. Additionally, serum antibody of these classes is also demonstrable. Antigen-specific memory cells are also recruited into the lung after primary immunization, and specific antibody may continue to be produced for several years after antigen exposure. This process may involve continued restimulation by antigen sequestered by pulmonary dendritic cells.
