Feeling old? A molecule called CD47 that cells put on their surfaces as a “Do Not Eat Me” signal may have a lot to do with poor functioning in old age.
NIH investigators and colleagues have discovered that when the immune system first responds to infectious agents such as viruses or bacteria, a natural brake on the response prevents overactivation. Their new study in mBio describes this brake and the way pathogens such as SARS-CoV-2, the virus that causes COVID-19, turn it on. Their finding provides a potential target for an immunotherapy that might be applied to a wide range of infectious diseases.
When a cell senses an infectious agent with molecules called pathogen recognition receptors, part of its response is to increase cell surface expression of a molecule called CD47, otherwise known as the "don't eat me" signal. Increased CD47 expression dampens the ability of cells called macrophages, the immune system's first responders, to engulf infected cells and further stimulate the immune response. Upregulation of CD47 on cells was observed for diverse types of infections including those caused by mouse retroviruses, lymphocytic choriomeningitis virus, LaCrosse virus, SARS CoV-2, and by the bacteria Borrelia burgdorferi and Salmonella enterica typhi.
