Too much alcohol dulls more than your wits. It also weakens your immune system and could make you much more

vulnerable to viruses, including HIV.

To see how alcohol affects resistance to infection, Gynogyi Szabo of the University of Massachusetts Medical School in

Worcester and colleagues exposed monocytes – white blood cells involved in the front-line defence against infection –

to chemicals that mimic viruses and bacteria. Half of the cells were also soused in the levels of alcohol that a person

might have in their blood after quaffing four or five alcoholic drinks daily for a week.

Alcohol blunted the monocytes’ defences. When the over-the-limit cells were exposed to a virus mimic, they produced

only a quarter as much of the virus-fighting signalling molecule called type-1 interferon as teetotal monocytes made.

“Interferon is pivotal, the first response to any viral infection,” says Szabo. “There’s no viral elimination without it.”

 

Lowered immunity

Monocytes exposed to a bacterial chemical suffered a double blow when inebriated. Not only did they make half as

much type-1 interferon as their abstemious equivalents, they also overproduced an inflammatory chemical called

tumour necrosis factor-alpha.

Although important for initiating inflammatory responses to bacteria, continued production of this chemical

can damage tissue.

Szabo says that the results fit with evidence from medical records that chronic heavy drinkers with HIV die sooner than

non-drinkers. They also fit with earlier studies showing that the immune system of heavy drinkers might be less vigilant

against cancer.

Szabo says heavy drinkers should beware of damaging their immune systems. Next, she hopes to see if alcohol makes

flu vaccinations less effective.

Mark Hutchinson of the University of Adelaide in South Australia says that the results tally with post-mortem data

showing that chronic drinkers have less immune chemicals in their blood than normal.

 

Brain and blood

In another study published this week, Hutchinson and his colleagues show in mice that the same monocytes, when

situated in the brain, may play a part in drinkers’ clumsiness.

“We’re dealing with brain immune cells, which appear to respond to alcohol differently from blood immune cells,”

says Hutchinson.

His team discovered that blocking an antibacterial receptor on monocytes in the brain stopped mice being so clumsy

when exposed to alcohol.

“It sure is a complicated story we’ve only scratched the surface of,” Hutchinson says