From growth factor dependence to growth factor responsiveness: The genesis of an alveolar macrophage cell line

Summary A rat pulmonary alveolar macrophage (PAM) cell line (NR8383) was initiated in culture in the presence of a gerbil lung cell conditioned medium (GLCM), and has been propagated continuously for over 36 mo. When examined at different times throughout this in vitro period, NR8383 exhibited characteristics typical of macrophages: (a) Zymosan ingestion was seen in 90 to 98% of the cells examined; (b)Pseudomonas aeruginosa phagocytosis in 50 to 80%; (c) Nonspecific esterase activity in >95%. During the first 6 mo., the PAM replicated with doubling times approximating 15 to 20 d. Throughout this period, GLCM dependence was evident. After 27 wk in vitro, NR8383 replication increased markeldy, and within 2 wk, the doubling time was less than 48h. NR8383 was readily monitored by ³H]thymidine (TdR) blastogenesis assay. In the presence of GLCM uptake of ³H]TdR was fivefold greater than in control cultures. Adherence and growth kinetics were effectively controlled by modulation of GLCM or serum content in culture medium. It was demonstrated that PAM growth factor(s) is ubiquitous, not species-specific, and under certain conditions, may be derived from “endogenous” sources of persisting non-PAM populations within the parent, uncloned line NR8383. Cloned progeny remain devoid of non-PAM “feeder” cells, but retain macrophage properties, including interleukin-1 secretion, Fc receptors, and H₂O₂ production. This work was supported in part by grants #A119811 and #HL25378, Project 1B, from the National Institutes of Health, Bethesda, MD.