Macrophages are able to memorize infections

The human body defends itself against viruses and bacteria with two types of immunity. Innate – reacts quickly but without a pinpoint hit, and adaptive – recognizes specific threats and produces antibodies. For a long time, it was thought that only adaptive defenses had memory, but recent discoveries have changed that view.

These white blood cells are the first to fight infection. It turns out that they are able to adapt to past encounters with pathogens. After contact with viruses or bacteria, macrophages readjust their work: in some cases, they become more aggressive, and in other cases – on the contrary, lose sensitivity to threats.

A group of scientists from the University of Chicago (USA) conducted an experiment, modeling the impact of different infections on macrophages. 80 variants of inflammatory signals of different intensity and duration were tested. It turned out that short contact with pathogens enhances the immune response, while prolonged exposure – on the contrary, reduces the activity of macrophages.

The discovery explains why patients who have suffered severe infections, such as sepsis, become vulnerable to new diseases. Their immune cells become accustomed to inflammation and stop responding effectively to pathogens. This can lead to complications and repeated infections.

Specialists have developed a model that allows predicting the behavior of macrophages depending on their previous experience. In the long term, this will help to regulate their activity – for example, to reduce excessive inflammation in autoimmune diseases or, conversely, to activate the cells when immunity declines.

So far, only the short-term effect of infections on macrophages has been studied, but it is assumed that changes in their work can persist for weeks. If this is confirmed, there will be a chance to create new strategies in the fight against chronic inflammation and severe infections.