Nat Immunol: a new mechanism of immunity increase after pulmonary infection

February 14, 2020 / Biovalley / according to the latest research of the Francesca Crick Institute, the immune system's response to respiratory tract infection is constantly changing, which depends on the history of previous unrelated infections The body has two kinds of immunity to infection Adaptive immunity provides immune "memory", which can react quickly and strongly when the same disease occurs more than once In contrast, innate immunity provides a broad and less specific first line of defense against all pathogens and is essential to control infections the body has not experienced before Photo source: https://cn.bing.com, a study published in the journal Nature Immunology, found that after recovering from respiratory tract infection, some cells in the innate immune system of the lung will more effectively provide additional protection against new infections in the next few weeks Specifically, they found that mice injected with the flu virus were significantly less likely to catch completely different bacterial infections a month later This increased immunity is the result of a particular type of immune cell entering the lung from the bone marrow during the initial infection, turning into a pulmonary macrophage (a white cell) Once in the lungs, these cells produce cytokines - hormone like molecules that cause inflammation and help fight pathogens Because these particular macrophages are still more active in the lungs after the infection has been resolved, they provide an additional layer of protection against future infections over the next few weeks However, over time, the ability of these macrophages to produce high levels of cytokines disappeared This means that after a few months, the ability to fight infection declines and eventually returns to levels in previously uninfected animals The researchers believe that this mechanism also applies to humans "Influenza is a serious disease, especially for vulnerable groups, so we are not saying that influenza infection is beneficial On the contrary, this study provides us with valuable insights on how a rapidly cleared virus infection can continue to affect immunity in the following weeks through long-term changes in innate immune cells This may partly explain why our response to disease is ever-changing - you can beat it asymptotically in a week, but in a few weeks it can have a serious impact, "said Helena aegerter, lead author and doctoral student at the immune regulation laboratory at the Francesca Crick Institute The researchers plan to further study how infection histories affect the immune system, including in cases such as asthma or chronic obstructive pulmonary disease, and the increased inflammatory response explained in this study may aggravate symptoms "The level of protection of our immune system is not constant This means that it is important for people to take long-term measures to prevent infection in appropriate places, such as winter flu vaccine Reference: Andreas wack et al Influenza induced monocyte derived alveolar macrophases confer prolonged characteristic protection, Nature Immunology (2020) Doi: 10.1038/s41590-019-0568-x