Lack of lice behind asthma?

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Published: 22 April, 2009, 16:41
Edited: 14 October, 2009, 11:01

Modern hygiene is to be blamed for the allergies epidemic we face today. Immunologists have established that lice contribute to priming the immune system in mammals to respond correctly to allergens.

The role of infections and intestinal parasites, like gut worms, in the development of the immune system is well-known. Our civilization helped get rid of many parasites and allows for the efficient treatment of germs, at least for the majority of people living in developed countries.

On the downside, without exposure to them in childhood, the immune system sometimes fails to tune itself properly, and overreacts to harmless things like certain types of food or pollen, i.e. shows an allergic response. This theory, called “hygiene hypothesis” is supported by a lot of empirical evidence, and is widely accepted as true by immunologists.

A new study by a team led by Jan Bradley, a parasitologist at Nottingham University, UK, suggests that the body parasites have their role in priming the immune system in mammals too. The findings are published in the BioMed Central journal BMC Biology and reported on by New Scientist magazine.

They trapped 100 wood mice infested with various worms, mites, ticks, fleas, and lice, and tested their immune response. As expected, the mice with roundworms, produced less tumour necrosis factor-alpha (RNF-alpha), a chemical regulating immune cells, than in their clean counterparts in response to the germs.

But, surprisingly, mice with heavy lice infestations showed even stronger immune suppression, producing half as much TNF-alpha as uninfested mice. The production of the chemical didn’t show correlation with other factors like age, sex, or other general conditions.

Bradley wants to check his observations by delousing the wild mice to see if the immune suppression in them and their descendants change accordingly.