Alveolar macrophages (AMs) are pivotal for maintaining the lung homeostasis, but how the development and function of AMs regulated remains largely unknown. In the present study, we demonstrated that the number of AMs was controlled by the Tsc1 protein. Cd11c-specific deletion of Tsc1 caused inefficient transition from pre-AMs to AMs in lung, which led to a great reduction of AM population. Ablation of Tsc1 downregulated the expression of surface marker CD64 and SiglecF on AMs. We further showed that conditional knockout of Tsc1 led to enhanced proliferation and increased reactive oxygen species (ROS) production and phagocytosis in AMs. These results indicated that Tsc1 was a critical regulator of development, proliferation and function in AMs. (C) 2018 Elsevier Inc. All rights reserved.