Immunity ‘forgotten’

German philosopher Friedrich Nietzsche is credited with the phrase ‘‘what does not kill me makes me stronger’’. More than 130 years later, two studies show that’s not true when it comes to catching measles. Instead, an encounter with the measles virus leaves people with a kind of ‘‘immune amnesia’’, making them more vulnerable to infection.

When certain cells in our body see a foreign invader like a bacterium or virus, they kill it, chop it into bits, and present those bits, known as antigens, to other specialised cells.

These specialised cells then make ‘‘antigenspecific’’ antibodies that protect us from future infection by those same viruses and bacteria.

Many vaccines bypass the invasion by virus or bacterium, presenting our immune system with the chopped up bits of antigen instead. This lets us get on with making antibodies while not having to fight the microbe at the same time.

During a measles outbreak in the Netherlands, families that refused vaccinations for religious reasons allowed researchers to take blood from their school-aged children before they had caught measles, and a few months later.

Some children had mild measles and others a more severe infection. Some children remained free of measles.

Researchers then measured the presence of antibodies to thousands of viral and bacterial antigens to get a snapshot of each child’s antibody repertoire before and after a measles infection.

They found that antibodies in the children’s blood samples disappeared after they caught measles. The amounts varied – some children lost one in 10 of their antibodies, others lost almost three-quarters.

The children who didn’t get measles did not lose antibodies. Neither did a group of vaccinated children.

In other words, infection with the measles virus seems to cause our body to ‘‘forget’’ the immunity it has developed to other infectious diseases in the past.

Worryingly, it also affects immune cells that are standing by ready to fight unfamiliar infections.

Getting the MMR vaccine protects ourselves, and all the vulnerable people in our community who can’t be vaccinated. It also preserves our ability to fight off all sorts of infectious diseases.

That’s a win.

Infection with the measles virus seems to cause our body to ‘‘forget’’ the immunity it has developed to other infectious diseases in the past.