Sleep may strengthen long-term memories in the immune system
Deep (slow-wave) sleep, which helps retain memories in the brain, may also strengthen immunological memories of encountered pathogens, German and Dutch neuroscientists propose in an Opinion article published September 29 in Trends in Neurosciences.
The immune system “remembers” an encounter with a bacteria or virus by collecting fragments from the microbe to create memory T cells, which last for months or years and help the body recognize a previous infection and quickly respond. These memory T cells appear to abstract “gist information” about the pathogens, allowing memory T cells to detect new pathogens that are similar, but not identical, to previously encountered bacteria or viruses.
Studies in humans have shown that long-term increases in memory T cells are associated with deep slow-wave sleep on the nights after vaccination. Taken together, the findings support the view that slow-wave sleep contributes to the formation of long-term memories of abstract, generalized information, which leads to adaptive behavioral and immunological responses.
The obvious implication is that sleep deprivation could put your body at risk. “If we didn’t sleep, then the immune system might focus on the wrong parts of the pathogen,” says senior author Jan Born of the University of Tuebingen.
“For example, many viruses can easily mutate some parts of their proteins to escape from immune responses. If too few antigen-recognizing cells [the cells that present the fragments to T cells] are available, then they might all be needed to fight off the pathogen.
In addition to this, there is evidence that the hormones released during sleep benefit the crosstalk between antigen-presenting and antigen-recognizing cells, and some of these important hormones could be lacking without sleep.”
Born says that future research should examine what information is selected during sleep for storage in long-term memory, and how this selection is achieved. This research could have important clinical implications.