Immunology of the lower respiratory tract. II. The plaque-forming response of canine lymphoid tissues to sheep erythrocytes after intrapulmonary or intravenous immunization.

Groups of dogs were immunized with sheep erythrocytes administered either directly into the lower respiratory tract (bronchoalveolar spaces) or intravenously. The hemolytic plaque-forming response (Jerne plaque assay) was studied in various canine lymphoid populations (bronchoalveolar cells, hilar lymph nodes, peripheral lymph nodes, and splenic and peripheral blood leukocytes) as a function of time after immunization and as a function of the dose of antigen administered. Serum hemagglutinating antibody titers against sheep erythrocytes were also measured. Intrapulmonary and intravenous administration of sheep erythrocytes to dogs both result in an immune response, the kinetics of which are identical to those observed in other animal species. At equivalent doses, the intravenous route is more efficient than the intrapulmonary route in generating serum hemagglutinating antibodies and antibody-forming cells. Both routes give rise transiently to circulating antibody-forming cells during the primary response; the distribution in tissues of antibody-forming cells is distinctive and unique, depending on the route of immunization. After i.v. immunization, antibody-forming cells are found predominately in spleen, blood, and bronchoalveolar spaces; after intrapulmonary immunization, they are located predominately in hilar lymph nodes, blood, and bronchoalveolar spaces. The reasons for this pattern of distribution are not known. Both routes of immunization are equally effective in populating bronchoalveolar air spaces with antibody-forming cells, which are predominately IgM-secreting and IgG-secreting cells. IgA-secreting cells were not detected.