Enhancement of systemic immune response by immunization into chronically inflamed lungs

Intrapulmonary instillation of proteins into rabbit lungs with BCG-induced granulomatous inflammation results in greater transport of these molecules into the blood, and the primary route is probably the pulmonary lymphatics. In addition, rabbits with inflamed lungs develop a more potent systemic immune response when exposed to soluble antigens as an aerosol. The current study was done to further study the mechanisms of this phenomenon using the Jerne plaque technique. Intrapulmonary immunization with soluble antigens (solubilized SRBCs and HSA) resulted in a greater PFC response to both antigens when the lungs exhibited BCG-induced granulomatous inflammation. A previous study demonstrated that more antigen administered intratracheally was found in the HLNs when the lungs displayed granulomatous inflammation. However, in the present study, we did not observe an enhanced PFC response in HLN cells when antigens were introduced into inflamed lungs. When rabbits with BCG-inflamed lungs were immunized i.v., they did not develop an enhanced PFC response in the spleen. Immunization into the respiratory tract of normal rabbits with large doses (300 micrograms) of soluble antigens also resulted in a substantial PFC response in the spleen that was quantitatively greater than that induced by the same i.v. dose. These data indicate that (1) administration of antigens into inflamed lung results in an enhanced systemic immune response, (2) although larger quantities of soluble antigens administered by the pulmonary route accumulate in the HLN when lungs are inflamed, cells from this tissue do not exhibit an enhanced PFC response, and (3) large doses of soluble antigens instilled into normal lungs induce a greater systemic immune response that the same doses administered i.v. This study further demonstrates the importance of pulmonary inflammation and the immune response to inhaled antigens and provides insight as to how individuals with chronic inflammatory lung disease can react in an augmented fashion to environmental antigens.