In comparison to primary immune responses after lung immunization, the level of antigen‐specific antibody and the number of cells producing specific antibody are significantly increased after challenging the lungs with antigen. The response of immune memory cells in the lung to an antigen challenge could be responsible for this elevated immune response. However, increased numbers of antibody‐producing cells, possibly produced in the lung‐associated lymph nodes, are also found in the blood after an antigen challenge. Therefore, it is possible that both the response of immune memory cells in the lung, and the recruitment of antibody‐producing cells from the blood, contribute to the elevated levels of antibody in the lung after an antigen challenge. This study compared the level of antibody produced in the lung by the response of pulmonary immune memory cells with the level of antibody produced by antibody‐forming cells that enter the lung from blood after an antigen challenge. This comparison was made possible by immunizing and challenging two lung lobes of dogs with two antigens. The immune responses to both antigens were then evaluated in both lung lobes after primary immunization and challenge. Data from these evaluations showed that most antibody in the lung after an antigen challenge is produced by a localized anamnestic response of pulmonary immune memory cells. A significantly lower level of antibody entered the lung from the vasculature and/or was produced by antibody‐forming cells that entered the lung from blood after an antigen challenge.