Autism is linked to childhood infections

Mutations are called the cause of autism, but this does not mean that if a child has an autistic mutation, he will definitely have autism. Whether a mutation works or not depends on additional factors, and one such factor is a severe infection in early childhood. UCLA researchers studied autistic mutations in a gene Tsc2 – various symptoms of autism can be found in about half of people who have mutations in Tsc2… The experiments were carried out on mice – although there can be no real autism in mice, some of its manifestations can also be observed in animals. When it comes to social behavior, mice can be made autistic.

Small mice on the third, seventh and fourteenth days of life were injected with a substance that mimics the virus. When the mice got older, they were put in a cage with another mouse they didn’t know. The experimental mice could stay in the empty half of the cage, or they could go to get acquainted. All mice spent most of their time next to their new friend. The next day they were again put in the same cage, but now on one side there was yesterday’s and already familiar mouse, and on the other – a new unfamiliar one.

In such a situation, ordinary mice go to get acquainted and spend more time with the new mouse than with the one they already know. However, mice with an autistic mutation that had been ill with the pseudovirus communicated equally with both neighbors. Everything looked as if the experimental mice were forgetting who they saw yesterday. When mice communicate, they squeak with ultrasound, and while at first glance, mice with the autistic mutation were as sociable as normal mice, their ultrasound signals were significantly shorter.

In an article in Science Advances it is said that after a pseudo-infection in the brain in mice, genes associated with interferons and microglia – the so-called auxiliary cells of the nervous system that perform the immune function – worked more actively in mice. If the microglia were temporarily killed, the mice began to behave as usual and continued to behave as usual after the microglia were restored. If, before pseudo-infection, interferon signals were turned off in one way or another in mice, they did not develop any abnormalities in behavior, despite the autistic mutation. Obviously, for the mutation to work, the body must experience an infectious shock in early childhood, strong enough to be remembered by the immune cells in the brain.

The authors of the work also analyzed more than 3.5 million case histories, and found that boys who had a serious infection between one and a half and four years, the risk of autism spectrum disorders increases by 40%. For girls, they failed to find a statistically significant link between infection and autism – at least in the medical data that the researchers had in their hands.

Exactly what mechanism works here remains to be seen, so for now it is worth talking only about the fact that autism spectrum disorders and childhood infections are related to each other. In general, the effect of immunity on autism is being studied quite actively: for example, we wrote about why inflammation during pregnancy increases the risk of autism in a child. But even here it is not so simple: two years ago, MIT employees published in Nature See an article that discussed how inflammation can temporarily weaken autism.

Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by

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