Splenic influence on the development of a local pulmonary immune response

The role of the spleen in the development of specific antibody-forming cells (sAFC) in the pulmonary draining lymph nodes (pdLNC) of hamsters after local inoculation of sheep erythrocytes (SRBC) was evaluated. The role of the spleen was viewed from two vantage points. Panels of animals were either splenectomized with appropriate sham-operated controls before intratracheal inoculation of SRBC, or panels were immunized intravenously simultaneously with the local inoculation of antigen. The presence of an intact spleen was not necessary for the induction of a sAFC response to occur in the pdLNC. Similar numbers of immunoglobulin M (IgM) sAFC were recorded in the pdLNC on day 4 of both sham-operated and splenectomized animals. However, an enhancement of this local response occurred on day 7 if the animals were systemically immunized and therefore demonstrated active participation of the spleen in the specific immune response. The results support the hypothesis that although a local response may occur in the pdLFC in the absence of a spleen or a splenic response, the presence of a systemic or splenic response appears to be important for the enhancement of local IgM sAFC response. These observations suggest that the immune defenses involved in the lower respiratory tract may differ from those in upper respiratory tract and other mucosally lined organs in that the response of the spleen to the antigen affects the local response to that antigen.