Induction of antigen-specific IgA-forming cells in the upper respiratory mucosa.

We investigated the actual processes for activating respiratory mucosal immunity. Hartley guinea pigs were immunized with particulate antigen of dinitrophenylated ovalbumin into the duodenum (group A), trachea (group B), and nasal cavity (group C) 1 week after systemic priming with the soluble antigen. The control animals (group D) received only systemic priming. Immunoglobulin A antibody titers in nasal secretions and saliva from groups A and B significantly exceeded those of groups C and D (p less than .01). Many antigen-specific IgA-forming cells were detected in the respiratory and gastrointestinal mucosae of groups A and B. Following duodenal immunization, the appearance of antigen-specific IgA-forming cells in Peyer's patches preceded those in mesenteric and hilar lymph nodes, while they simultaneously appeared in the lymphoid tissues after tracheal immunization. These findings suggest that intratracheal immunization mainly stimulates bronchus-associated lymphoid tissue as a source of IgA precursors, as intraduodenal immunization stimulates gut-associated lymphoid tissue.