FATE AND CONSEQUENCE OF AN ORGANIC PARTICULATE ANTIGEN INSTILLED INTO BRONCHOALVEOLAR SPACES OF NORMAL CANINE LUNGS

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Abstract
Radioiodinated sheep red blood cells were deposited by catheter in bronchoalveolar spaces of normal dogs to investigate basic mechanisms of antigen processing by the lung and to characterize the tissue distribution of cells producing antibody against this organic particle. Histologically, instillation of sheep erythrocytes produced a localized, self-limited inflammatory consolidation. The mechanisms of disposal of the organic particle were complex. Most sheep erythrocytes were removed by phagocytosis and digestion. Initially alveolar macrophages and subsequently neutrophils and eosinophils participated in these processes. Radiotracer studies demonstrated rapid systemic release of soluble erythrocyte components from bronchoalveolar spaces. The soluble material was in macromolecular form, appeared immediately in the serum, and accumulated rapidly in the liver. The data suggested that only a tiny fraction of the released soluble material was related to the antigenic determinants of intact sheep erythrocytes. Small but significant amounts of insoluble radioactivity were found firmly associated with nucleated cells in lung and hilar lymph nodes, but not with cells in spleen or peripheral lymph nodes. Cells producing antibody against sheep erythrocytes were most concentrated in hilar lymph nodes. These data suggest that transport of material in immunogenic form from pulmonary air spaces to hilar nodes is important for initiation of humoral immune responses in the lung to organic antigens. The observations may be pertinent to antigen processing after inhalation of organic particles into the lung.