Senile memory of T-lymphocytes
Scientists have found out why flu and COVID-19 are more difficult to tolerate with age
Australian scientists have found out why older people are particularly susceptible to respiratory pathogens — pulmonary viral infections, including the new coronavirus SARS-CoV-2. The results of the study are published in the journal Clinical & Translational Immunology (Nguyen et al., Influenza, but not SARS‐CoV‐2, infection induces a rapid interferon response that wanes with age and diminished tissue‐resident memory CD8+ T cells).
It is known that elderly people are very susceptible to viruses, and lung infections in them often lead to serious consequences and life-threatening complications. Scientists assumed that this was due to an age-related decline in the functions of the immune system, which is called immune aging. However, until now it was unclear why immunity to pulmonary pathogens falls in the first place.
Researchers led by Linda Wakim from the Peter Docherty Institute of Infections and Immunology at the University of Melbourne, using lung tissue samples from donors aged 22 to 68 years, assessed how the immune cell landscape in human lungs changes during life, and also studied in laboratory experiments how immune cells respond to exposure influenza viruses and SARS-CoV-2. None of the donors were ill before the COVID-19 study.
The results showed that while the immune cells of most species remain stable throughout life, the number of CD8+ memory T cells decreases with age. Particularly susceptible to immune aging were tissue-resident memory T cells, or TRM cells, which are a line of T cells that are present in the tissues of the skin, lungs, and gastrointestinal tract.
The authors found that when lung tissue was infected with influenza virus in elderly people, there was an age-related weakening of the antiviral immune response, expressed in a decrease in the production of type I interferons, polypeptide cytokines GM-CSF and, especially, gamma interferon, which is produced by CD8+ memory T cells.
According to researchers, a slower immune response to influenza infection in older people is due to the fact that T cells specific to fighting the flu virus are lost with age, and memory cells give out fewer "emergency" signals from infected cells.
As for SARS-CoV-2, the immune response was weak in all samples, regardless of age. The authors explain this by the fact that the new coronavirus is in all cases unknown to the immune system, it has not encountered it before, and it lacks specific immune cells that could fight it.
According to the researchers, the main reason for the decrease in immunity to lung infections in older people is the depletion of pathogen-specific TRM cells in the lungs with age, which leads to a violation of the early antiviral immune response.
The authors believe that their results make an important contribution to the understanding of age-related changes occurring in the landscape of immune cells of the lungs, and will potentially allow the development of strategies for preserving the tissue memory of CD8+ T cells and reduce the vulnerability of older people to respiratory infections.
Portal "Eternal youth" http://vechnayamolodost.ru