Allergies are a type of inappropriate immune response, where our
bodies misidentify a harmless substance as a threat.
For a long time, we've been aware that allergies occur much more
frequently in Western countries, but we don't know why this is. One
idea that has grown in popularity is the hygiene hypothesis, which
suggests that our immune systems need to come into contact with a range
of micro-organisms when we are young to be able to produce appropriate
immune responses later in life.
‘A molecular mechanism that could explain why allergies are less common in developing countries has been discovered by researchers.’
Researchers have discovered a molecular mechanism that could explain
why allergies are less common in developing countries. Writing in the
, they report that this finding could be the first step to developing new immunotherapies to prevent allergies.
Dr Joseph Igetei, formally of the University of Nottingham, UK, now at
the University of Benin, Nigeria, said, "We know that worm infections occur
more frequently in less developed countries, i.e. in places where
allergies are rare. Although it's been suggested that worm infections
could prevent against different allergies, there has been little
concrete evidence of the potential molecular mechanisms that might
mediate any such relationship."
In this study, the research team led by Professor Mike Doenhoff from
the University of Nottingham, and including Dr Joseph Igetei, Dr Marwa
El-Faham from Alexandria University and Dr Susan Liddell, set out to
discover if the antigens produced by a common species of parasitic worm
that infects humans (called Schistosoma mansoni
cross-reactive to antigens from peanuts, i.e. do the proteins from the
worm and from the peanuts trigger the same immune response?
investigate this, they used antibodies from rabbits that had been
exposed to various life stages of the worm - antibodies are a type of
immune protein made by the body to provide a tailored response to any
substance deemed to be a threat. The researchers tested if these
antibodies (which had been produced specifically against the parasitic
worm) also reacted to various proteins found in peanuts.
They found that the antibodies responded to several proteins in the
peanut, in particular one called Ara h 1, which is known to be a key
player in inducing the negative response in people who are allergic to
"It may sound strange that peanuts and worms have anything in common
that could cause the immune system to generate the same response," said
Professor Mike Doenhoff. "However, our work indicates that proteins
from these two seemingly very different organisms actually have
identical markers on them, meaning the immune system views them in the
same way and targets them with similar antibodies."
These findings are important in two ways. Firstly, this work goes
some way to explaining the molecular mechanisms behind the observation
that countries with a high incidence of worm infections have a low
incidence of allergy. Although more work is needed to confirm the exact
relationship, the team think that antibodies produced in response to a
worm infection could stop the immune system from producing an allergic
reaction when faced with a novel substance such as peanut protein.
Secondly, this work may lead to new ideas to treat allergies. The
team's next step is, however, to see if antibodies produced by humans in
response to a worm infection also cross-react with peanut proteins.