Influence of Age on Mouse Pulmonary Alveolar Macrophage Clonal Growth

Abstract

Although monocyte influx has been suggested as the primary source of pulmonary alveolar macrophages (AM), increasing evidence from recent studies has indicated that AM may be sustained through a self-renewal mechanism. We evaluated the age-related changes of the clonal growth (colony formation) of AM in mice (C57BL/6N mice and senescence accelerated mice). The colony forming unit (CFU) of AM of 24 month old C57BL/6N mice was lower than that of AM of 4-month-old mice (p< 0.05). In SAMP6 (senescence accelerated mice), CFU of AM was decreased with aging (p<0.05). In SAMR1 (controls for SAMP6), CFU of AM was decreased with aging (p<0.001). In SAMR1, CFU of bone marrow (BM) adherent cells of 12-month-old mice was similar to that of 4-month-old mice. In SAMP6, CFU of BM adherent cells of 12-month-old mice was larger than that of 4-month-old mice (P< 0.005). It was concluded that the CFU of AM declined with aging, but the CFU of the BM adherent cells did not. The decline of the AM CFU may be partly responsible for the defect of the immune response of the alveolar space in the elderly. © 1994, The Japan Geriatrics Society. All rights reserved.