Men really do have an excuse for supposedly being wimpy¹ about coughs and colds - their immune systems are not as strong as women's, research suggests.

调查显示，男人在理论上患咳嗽和感冒概率大点--他们的免疫系统没有女人的强。

The weaker sex?

A Canadian study indicates that the female sex hormone² oestrogen（雌激素） gives women's immune systems added bite at fighting off infection.

Oestrogen seems to counter an enzyme³（酶） which blocks the inflammatory process（炎性过程）.

The McGill University study appears in Proceedings⁴ of the National Academy of Sciences.

The researchers focused on an enzyme called Caspase-12, which is known to put a brake on the inflammatory process, the body's first line of defence against harmful invaders⁵ such as bacteria and viruses.

They worked on mice that lacked the Caspase-12 gene⁶, and were thus extremely resistant⁷ to infection.

The human Caspase-12 gene was implanted into a group of male and female mice, but only the males became more prone⁸ to infection.

The researchers concluded that oestrogen produced by the female mice blocked the expression of the human Caspase-12 gene.

They were also able to locate the precise place where oestrogen binds⁹ to the gene in order to block its activity.

Since the experiments were conducted using a human gene, the researchers are confident their work is applicable to humans.

Lead researcher Dr Maya Saleh said: "These results demonstrate that women have a more powerful inflammatory response than men."

The researchers believe women may have evolved a more robust¹⁰（强壮的，强健的） immune system because of their key role in producing and nurturing¹¹ young.

Their work raises the possibility of new ways to reinforce the immune system using genetic¹² manipulation（处理）.

But writing in the journal, the researchers said: "A question remains¹³: will men be amenable¹⁴ to（服从） the idea of being treated with an exclusively female hormone?"

Dr Leslie Knapp, of the University of Cambridge, said there was a substantial body of evidence to show that women were better at fighting infections than men.

She said: "Women are well known to be able to respond more robustly¹⁵（粗鲁地） to infections, and to recover more quickly than men.

"In evolutionary¹⁶ terms it only takes one male to reproduce with lots of females, but females are much more important in terms of producing offspring."