Deep sleep boosts immunological memory
It is widely accepted that sleep helps to form long-term memory. Now, scientists from the University of Tuebingen in Germany have proposed that deep sleep may strengthen not only psychological but also immunological memories. In an article published in Trends in Neurosciences, the researchers suggest that slow-wave sleep (SWS), also known as deep sleep, may strengthen immunological memories of previously encountered pathogens, in a system that shares some features with psychological memory.
They explain that without memory, innate response patterns would be insufficient to enable an organism to survive in a changing environment, and they argue that this is true both for the mind and body. In the formation of psychological memory, the central nervous system (CNS) mediates responses to psychological events and forms lasting neuronal memory representations of relevant features of the physical and social environment. The same, they say, happens with the immune system. The system is able to form long-lasting memories, which store key features of antigens in the T- and B-cell systems, enabling a faster, more effective response when re-encountering the antigen. T and B cells are highly specialized cells that defend against disease. Antigens are proteins found on the surface of pathogens.
When the immune system meets a bacteria or virus, it encodes it, collecting enough information to create memory T cells. These memory T cells will help the system to recall the same bacteria or virus in future and to be better prepared to fight the attack. The researchers argue that consolidation of the information happens during SWS.
It is also proposed that T cells would collect gist information rather than detailed information about pathogens, so that they can recognize not only the exact virus or bacteria next time, but similar ones also.
Senior author Prof. Jan Born says that if the T cells did not store gist information, the immune system might ultimately focus on the wrong part of a pathogen after a virus mutates some parts of its protein. Studies have shown that after a vaccination, there are long-term increases in memory T cells which are associated with SWS. This supports the view that SWS contributes to the formation of long-term memories of general information, leading to adaptive behavioral and immunological responses.
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