28 October 2011

Infections of newborns permanently disrupt the brain

The results of earlier work by associate Professor Staci Bilbo from Duke University showed that laboratory rats that had infectious diseases in infancy develop an aggressive immune response in response to subsequent infections, negatively affecting the cognitive abilities and memory of animals.

In search of the reasons underlying this pattern, Bilbo and her colleagues found out that excessive synthesis of the signaling molecule interleukin-1 (IL-1) by microglia – specialized immune cells of the brain playing the role of phagocytes in response to infection can lead to a violation of the ability of laboratory animals to learn and memorize.

For almost 10 years, researchers have conducted a series of experiments in which they infected newborn rats with pathogenic bacteria, and in later adulthood subjected them to secondary infection with killed microorganisms – unable to cause disease, but a source of antigens familiar to the immune system. It turned out that against the background of an exceptionally effective immune response, such a secondary effect significantly worsened the ability of animals to learn and memorize. At the same time, scientists were surprised by the fact that even peripheral secondary infections that were not directly related to brain tissue triggered excessive synthesis of interleukin-1 by microglial cells.

To study the effect of the immune response on the ability to remember, rats were placed in a new environment for them and affected by a loud sound or a weak electric current. Ordinary animals memorized the situation from the first time and immediately froze at the second placement in the conditions associated with the shock effect. However, rats who had an infectious disease at an early age and were prone to excessive production of interleukin-1, in the described situation behaved as if they had first come into an environment accompanied by a painful effect.

Even in the absence of secondary infection, premature extinction of cognitive function, very similar to the development of Alzheimer's disease, was characteristic of animals that had an infection at an early age.

Experts believe that the data obtained explain the increased predisposition of some people to the development of neurodegenerative diseases. Knowledge of this mechanism can help in the development of new methods of diagnosis, prevention and treatment of such pathologies.

According to Bilbo, any disease that triggers an immune response worsens the cognitive abilities of a person whose body enters a kind of recovery mode. However, in animals that had infectious diseases at an early age, there was a stable change in the nature of the immune response, negatively affecting the state of their brain. The age at which the animals were infected roughly corresponds to the third trimester of human pregnancy, but Bilbo emphasizes that there is still too little data to extrapolate the results to humans.

The researchers suggested that an infection suffered at an early age causes irreversible changes in gene expression. Currently, they are studying the role of microglia cells in the formation of dependence, as well as the relationship between maternal care for a newborn and the functioning of its immune system.

Article by Lauren L. Williamson et al. Microglia and Memory: Modulation by Early-Life Infection is published in the Journal of Neuroscience.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Duke University:
Source Found for Immune System Effects on Learning and Memory.


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