Immunology of the lower respiratory tract. III. Concentrations of antigen and of antibody-forming cells in pulmonary and systemic lymphoid tissues of dogs after intrapulmonary or intravenous administration of sheep erythrocytes.

The distribution of antibody-forming cells to sheep erythrocytes among canine pulmonary and systemic lymphoid tissues differs distinctively depending on whether antigen is administered by the intrapulmonary or the intravenous (i.v.) route. After local (intrapulmonary) immunization, antibody-forming cells are restricted to the lung and regional lymph nodes; after i.v., they are widespread. To test the hypothesis that the tissue distribution of antigen is an important determinant of the resultant distribution of antibody-forming cells, dogs were immunized with radioiodinated sheep erythrocytes, either intrapulmonary (i.p.) or i.v. After 4 days, the concentrations of tissue-bound radioactivity and of antibody-forming cells in various lymphoid tissues were compared. The distribution of tissue-bound radioactivity among lymphoid tissues was clearly determined and different depending on the route of immunization. After i.p. administration, radioactivity was bound to lung and hilar lymph nodes; after i.v., it was found in the lung, liver, spleen and occasionally hilar nodes. Antibody-forming cells appeared in those lymphoid preparations which contained tissue-bound radioactivity. The exception was that locally applied antigen elicited antibody-forming cells in the lung poorly, despite the fact that abundant antigen remained localized to the lung. Notably, i.v. immunization resulted in the appearance of both antibody forming cells and cell-bound radioactivity in the lung. It is concluded that the distribution of antigen among tissues is a major determinant of the distinctive patterns of appearance of antibody-forming cells after different routes of immunization.