Antigen-specific down-regulation of bronchial reactivity in rats sensitized daily without adjuvant

Daily sensitization with ovalbumin (OA) and dog serum albumin (DSA) without adjuvant was performed in rats for 2-week periods. When the antigen was administered subcutaneously (s.c.), antibody responses were induced, as assessed in serum and bronchial lavage, and strong increases in transpulmonary pressure (TPP) after intravenous (i.v.) challenge with antigen. Sensitization without adjuvant with antigen as aerosol for similar periods also evoked pronounced antibody formation, although only weak increases of TPP were seen after challenge. Animals sensitized s.c. with OA and simultaneously exposed to OA as aerosol exhibited suppression of the TPP increase after challenge, whereas the antibody responses were not affected to any great extent. In contrast, the increase of TPP after challenge in animals similarly sensitized s.c. with DSA were not suppressed by OA given simultaneously as aerosol or vice versa.