The effects of age on immune responses in the antigen-instilled dog lung. Antibody responses in the lung and lymphoid tissues following primary and secondary antigen instillation.
To evaluate the effects of age on immunity induced by lung immunization, 11 aged (12-17 years; median age = 14) and 12 young (2-5 years) male Beagle dogs were instilled with 10 mg of keyhole limpet hemocyanin (KLH) in the right cardiac lung lobe and 10(10) sheep red blood cells (SRBC) in the left cardiac lung lobe. Five aged and six young dogs were sacrificed at day 9 after primary antigen instillation. The remainder were given challenge antigen instillations of KLH and SRBC at day 21 and sacrificed 7 days later. Serum, bronchoalveolar lavage fluid and lung tissue from immunized and control lobes, tracheobronchial, mesenteric and popliteal lymph nodes, spleen, and blood were taken at sacrifice. Anti-KLH IgA, IgG and IgM antibody production by cells in lung tissue and lavage fluid from the KLH-exposed lobe was lower at primary immunization and challenge in aged than young dogs. Lavage fluid IgA and IgG levels from the KLH exposed lobe at primary immunization and challenge were lower in aged versus young dogs, while IgM levels were lower only after primary immunization. Localized lung immune memory responses were also markedly lower in aged dogs when compared with young dogs. Anti-SRBC responses were similar to the anti-KLH responses. Our data show that systemic immune responses are significantly lower in aged dogs following primary antigen instillation, but not after antigen challenge in the lung. This was not the case for localized lung immune responses, which were significantly lower in aged dogs even following antigen challenge. The data also show that antibody production by lavage cells is a good index of interstitial lung cell antibody production.