Europe South Asia Asia Pacific Americas Middle East Africa BBC Homepage World Service Education
BBC Homepagelow graphics version | feedback | help
BBC News Online
 You are in: Health
Front Page 
World 
UK 
UK Politics 
Business 
Sci/Tech 
Health 
Medical notes 
Background Briefings 
Education 
Sport 
Entertainment 
Talking Point 
In Depth 
AudioVideo 
Thursday, 20 January, 2000, 19:09 GMT
Immune system 'causes miscarriage'

Foetus The foetus contains foreign genetic material


Scientists have moved closer to identifying the malfunction in a mother's immune system that causes some to miscarry..

They now believe that the lack of a single protein may lead to the immune system mistakenly identifying a developing foetus as a foreign invader and targeting it for destruction.

Working with mice, the researchers have identified an immune system protein called Crry which appears to play a crucial role in ensuring that babies are not killed before birth.

This protein is thought to de-activate a part of the mother's immune system to stop it attacking the developing embryo.

Similar proteins are suspected of playing the same role in humans.

A team from Washington University School of Medicine in St Louis, US, has shown that mice bred to lack Crry are unable to give birth to live young.

Instead, their immune system unleashes a destructive attack on the tissues of the developing foetus, which are dismantled and reabsorbed by the mother - the equivalent of a miscarriage in humans.

The researchers discovered that Crry blocks a branch of the mother mouse's body defences called the complement system, which helps destroy foreign material such as infectious organisms.

Crry prevents two other "complement" proteins from marking out cells for immune system destruction.

The researchers studied the cell make-up of foetuses growing in the mice that lacked Crry.

Activated for destruction


Lab mice Research was carried out on mice
They found that by the seventh day of gestation both the outer cells of the embryo and the cells of the developing placenta carried activated complement proteins.

They also found that immune system cells called neutrophils had invaded the complement-targeted tissue.

After 10 days it was clear that the immune system was destroying the embryos.

Dr Molina said: "Without this single molecule, complement components of the mouse immune system are activated, resulting in embryonic death."

The researchers, who reported their findings in the journal Science today, now plan to investigate the role of similar proteins in women's miscarriages.

Two placental proteins perform the same duties as Crry in humans - decay accelerating factor and membrane cofactor protein.

Their role in miscarriages has not been previously addressed.

Dr Molina said: "Using the mouse studies as a framework, we can jump to human studies and see whether miscarriages in women also involve complement regulation."

The work will focus on women who have auto-immune diseases such as lupus erythematosus and multiple miscarriages.

The team will try to determine whether such women have reduced levels of the Crry-like regulatory proteins, and might benefit from receiving them artificially.

Dr Gill Vince, an expert in miscarriage from Liverpool University, said most spontaneous abortions were a one off, but a small group of women suffered repeated miscarriages, around 60% of which were unexplained.

She said: "Any breakthrough in explaining repeated miscarriages is good, but it can be difficult to extrapolate from mice to humans as they have different placental systems."

Search BBC News Online

Advanced search options
Launch console
BBC RADIO NEWS
BBC ONE TV NEWS
WORLD NEWS SUMMARY
PROGRAMMES GUIDE

See also:
10 Jun 99 |  Health
Miscarriage risk of slow eggs
13 Jan 00 |  Health
Genetic miscarriage risk
25 Nov 99 |  Health
Caffeine blamed for miscarriages
02 Sep 99 |  Health
Couples 'need more support after miscarriage'
30 Jul 99 |  Health
Miscarriage prevention therapy 'does not work'

Internet links:

The BBC is not responsible for the content of external internet sites
Links to other Health stories are at the foot of the page.


E-mail this story to a friend

Links to more Health stories