IMMUNOLOGICAL STUDY OF LUNG DEVELOPMENT IN THE MOUSE EMBRYO .2. 1ST APPEARANCE OF THE GREAT ALVEOLAR CELL, AS SHOWN BY IMMUNOFLUORESCENCE MICROSCOPY

An antiserum that specifically recognizes a lung-specific antigen present in the great alveolar cell in the adult mouse lung was used in immunofluorescence studies to detect the first appearance of this antigen in the embryo. Cellular fluorescence was found to occur in the lung tissue from about Day 14.2 onward and to be due to the presence of the lung-specific or a related antigen. The simultaneous appearance of this antigen (ca. Day 14.2) and the cuboidal type of epithelial cell in which it occurs (ca. Day 14) means that the great alveolar cell-or its precursor-is first detectable around Day 14.2. Since the great alveolar cell-or its precursor-is the first and only type of alveolar epithelial cell to occur in the embryonic lung, it must be the stem cell from which the small alveolar cell derives. The persistent sharp demarcation between the prospective alveolar and bronchial epithelia indicates that the respiratory and the conducting portions of the lung originate from different parts of the tubular system in the prenatal lung. © 1979.