The Origin of Pulmonary Alveolar Macrophages

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Abstract
Pulmonary alveolar macrophages (PAMs) constitute a major lung cellular defense mechanism. There is still considerable controversy concerning the cellular precursors of the resident PAM population. Genetically related (RF/AI( + ) and RF/AI(-) substrains of mice were used to investigate the possibility of PAM origin from marrow stem cells. The RF/AI( +) mice carry a nonspecific readily identifiable prealbumin esterase marker, Es-2. Reciprocal chimerism was produced by administering a lethal dose of x-irradiation to (1) RF/AI(-) mice and subsequently injecting them with RF/AI( + ) bone marrow, and (2) RF/ Al( +) mice and subsequently injecting them with RF/AI(-) bone marrow. Eight weeks after irradiation pulmonary macrophages were obtained by bronchial lavage. PAMs from RF/AI(-) animals transplanted with RF/AI( +) bone marrow showed the prealbumin esterase marker, Es-2, while PAMs from the RF/AI( + ) animals given RF/AI(-) bone marrow had all but lost their Es-2 marker band, which confirms the marrow origin of PAMs.