Wednesday, June 27, 2012

Immunity vs. fertility

According to a Princeton University study, strong immunity is key to a long life, but it may be at the expense of fertility.

For 11 years, scientists studied a wild population of sheep (Soay), located on a remote island off the coast of Scotland. They tested the animals for levels of antibodies (e.g. to influenza and parasitic worms).

The sheep whose blood contained the most antibodies lived the longest. They were more likely to survive a harsh winter. However, they failed to produce as many offspring as other sheep.

Sheep with lower levels of antibodies tended to die earlier, but they gave birth to more lambs each year. Overall, there was a balance between immunity and fertility, as the differing groups of sheep produced the same number of progeny over their life times.

The results may explain why vaccines work better in some than others and why some get sicker than others when exposed to the same infection.


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