2 Comments »Posted on Wednesday 13 May 2009 at 9:16 pm by Jacob Aron
In Health & Medicine

Men prone to exaggerating their suffering when struck down with a cold often jokingly refer to “man flu” – the implication being that the illness is much more severe than anything their unsympathetic wives and girlfriends might catch. Perhaps men are owed an apology however, as a Canadian study has shown that male immune systems may not be as strong as women’s.

Scientists at McGill University discovered that the female sex hormone oestrogen can stop an enzyme from interfering with the body’s defences against bacteria and viruses. The enzyme Caspase-12 stops the natural inflammatory process which works to fight off infections, so the researchers used mice to find out how it works.

By implanting the human gene for Caspase-12 in to mice they discovered that the males became more prone to infection. The females however retained the natural resistance of mice without the Caspase-12 gene. Lead researcher Dr Maya Saleh and her colleagues concluded that oestrogen in the female mice were responsible for the difference.

“These results demonstrate that women have a more powerful inflammatory response than men,” she said. The team are confident that their research will also apply to humans, because they used a human gene.

They suggest that women could have evolved a better immune system because their health is key to being able to reproduce, a view shared by Dr Lesley Knapp, of the University of Cambridge:

“Women are well known to be able to respond more robustly to infections, and to recover more quickly than men.

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

The research could lead to new immune system aids through genetic manipulation. But then how would men complain when they got the sniffles?


  1. 2 Comments

  2. I’m not apologising!

    By Lottie on Wednesday 13 May, 2009 at 9:46 pm

  3. Whoever thought of attaching the man flu hook to this research is an evil PR genius. I’m confused though: Aren’t the symptoms of man flu (and cold and flu generally) largely a result of the immune response? So if women have stronger immune responses than men, they should have more severe symptoms?

    The evolutionary explanation smacks of fallacious group selectionist thinking. It sounds like Dr Knapp is saying that females have evolved stronger immune responses because the species or group can get by with a small number of men. But novel adaptations proliferate because of advantage to the individual, not the group.

    If the sex differences in the inflammatory response is adaptive, it would suggest that women are under more pressure than men to avoid infection, not that the species is under more pressure to protect women.

    But maybe caspase-12 expression is regulated by oestrogen for other reasons. I’m unclear on why we express caspase-12 in the first place if switching it off is really such a great idea. I can’t find the original paper, but incidentally I’d like to know whether they tested the effect of administering oestrogen to the male mice.

    By Sam Wong on Thursday 14 May, 2009 at 12:53 pm

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