ROGUE white blood cells infected with viruses can cause a range of serious
diseases, claim US scientists.
These renegade macrophages may figure in AIDS, cancer, dementia and even
heart disease, say researchers from SLIL Biomedical in Madison, Wisconsin. They
will present their evidence at a conference in London later this month.
Some immunologists say the theory is plausible. However, experts contacted by
New 杏吧原创 said that they would reserve judgement until the results
appear in the scientific literature.
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Macrophages are the immune system鈥檚 infantry, killing invaders by engulfing
them. Steve McGrath and Brian Herndier, who helped to found SLIL, think
macrophages can go berserk when infected by latent viruses. These viruses insert
their own genes among those of the cells they infect.
The researchers found that macrophages only run riot when the viruses鈥� DNA
ends up in specific genes. 鈥淚t鈥檚 random insertion, and 99 per cent of the time,
these viral insertions cause no problems,鈥� says Peter Molloy, chief executive of
SLIL. 鈥淏ut when they enter the genes [we鈥檝e identified], you get a cascade of
effects which result in disease,鈥� he says.
McGrath and Herndier made their discovery when investigating AIDS-related
lymphoma, a form of blood cancer that often affects patients with advanced HIV
disease. They spotted strange macrophages imbedded in tumours which, unlike
their normal counterparts, were multiplying rapidly. They called them ProMacs,
short for 鈥減roliferating macrophages鈥�.
They found that HIV had stowed its DNA in c-fes, a gene that can
cause cancer if damaged. Molloy says that when the stowaway DNA activated the
oncogene, the macrophages multiplied and produced growth factors. They think
these substances prompted nearby white blood cells called lymphocytes to
multiply and form tumours called lymphomas.
Further lab tests suggested that ProMacs are also present in the blood of
some HIV-negative people with arterial disease and dementia. The researchers say
that these rogue macrophages will kill healthy brain cells, for example.
Molloy thinks substances produced in large amounts by proliferating ProMacs
may either accelerate the growth of surrounding cells, causing cancer, or damage
tissue in the case of dementia.
Siamon Gordon, a macrophage expert at Oxford University, notes that some
cancers are known to 鈥渟ubvert鈥� macrophages to protect rather than attack tumour
cells. However, he questions why ProMacs would congregate at the disease site,
be it the brain or a blood vessel wall.
鈥淭he idea that macrophages could be triggered to be dangerous is a perfectly
plausible model,鈥� adds Mario Stevenson, a molecular biologist who studies HIV at
the University of Massachusetts Medical School in Worcester. But he says that
viruses insert their DNA into oncogenes extremely rarely. 鈥淯ntil it鈥檚 published
and I see all the data, I would treat it with scepticism,鈥� he says.