Dr.in Simona Saluzzo
MedUni Vienna RESEARCHER OF THE MONTH, January 2018
At the moment of birth, the lungs are exposed to the external environment and therefore need to protect themselves from damage and infection. We investigated the homeostatic role of the epithelium-derived alarmin interleukin-33 (IL-33) in new-born mice and discovered the immediate upregulation of IL-33 from the first day of life, closely followed by a wave of IL-13- producing type 2 innate lymphoid cells (ILC2s), which coincided with the appearance of alveolar macrophages (AMs) and their early polarization to an IL-13-dependent anti-inflammatory M2 phenotype. ILC2s contributed to lung quiescence in homeostasis by polarizing tissue resident AMs and induced an M2 phenotype in transplanted macrophage progenitors, at the cost of a delayed response to Streptococcus pneumoniae. These data highlight the homeostatic role of ILC2s in setting the immunological threshold in the lung and its implications in anti-bacterial defences.