Immunity: Uncover the molecular mechanisms and diversity mysteries of macrophage development in the lungs

The structure of the lungs often exposes them to viruses and bacteria in the air and blood.
macrophages are special immune cells that protect the lungs from such attacks, but in some cases macrophages in the lungs may cause serious lung diseases such as COPD and COVID-19.
so far, scientists have studied the developmental mechanisms of macrophages in the human lungs very limited.
have different origins and developments, in which cells such as white blood cells and monocytes are divided into the main types of genetic decisions.
in human organisms, two of which are classic CD14 plus monocytes and non-classical CD16 plus monocytes. In the
study, researchers used a new model to study the development of macrophages in the lungs directly in living lung tissue, combining the model with RNA sequencing, a technique that studies gene activity in a single cell, to reveal how monocytes in the blood are transformed into macrophages in the human lung. 'In this study, we revealed that the classic monocytes can migrate to trachea and lung tissue and convert them into macrophages to protect the health and function of the lungs,' said
researcher Tim Willinger, in addition to identifying a single-nucleal cell called HLA-Drhi, an intermediate type of immune cell between blood monocytes and trachea macrophages that can leave the blood circulation and migrate to lung tissue.
, however, non-classical monocytes can develop into macrophages in many blood vessels in the lungs and do not migrate to lung tissue.
Specific macrophages in the lungs may be associated with the occurrence of a variety of serious lung diseases, such as respiratory infections, in which monocytes in the lungs develop into macrophages that can help ward off bacteria and viruses, but certain types of macrophages may promote severe inflammation and infection in the body.
infections caused by SARS-COV-2, the researchers found that protective anti-inflammatory macrophages may be replaced by inflammatory lung macrophages from blood cells.
in other studies, researchers have found that the presence of macrophages derived from these blood monocytes is directly related to the severity of the disease in patients with COVID-19, as well as to the extent of lung damage. In patients with severe
COVID-19, levels of HLA-Drhi monocytes tend to be lower, mainly because they migrate from the blood to lung tissue, and given their important role in rapid inflammatory response, the researchers note that future development of new therapies may focus on inflammatory macrophages and monocytes to reduce lung damage and mortality in patients with severe COVID-19.
original source: Elza Evren, Emma Ringqvist, Kumar Parijat Tripathi, et al. Distinct developmental pathways from blood monocytes generate human lung macrophage diversity, Immunity (2020). DOI:10.1016/j.immuni.2020.12.003。