Colds: Why some don't get a runny nose

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MunichEven if everything around them is coughing and sniffing, some people stay healthy. Others catch every cold. US researchers have now found a possible cause for the different susceptibility to infection: the decisive factor is the biological age of special immune cells.

Provoked virus attack

For the experiment, Sheldon Cohen's team from Carnegie Mellon University recruited 152 volunteers between the ages of 18 and 55, who sprayed a solution containing a cold virus into their noses. The participants then went into quarantine for five days.

A total of 22 developed cold symptoms during this time. A further 82 had antibodies against the virus in their blood - they too had become infected without the disease having broken out. 47 of the participants were not infected.

Biological cell age is decisive

The scientists found a possible cause for the different susceptibility to infection when they examined the biological age of the participants' immune cells. This can be seen from the length of the so-called telomeres. These are protective caps that sit on the ends of the chromosomes. Each time a cell divides, they get a little shorter. If the telomeres are too short, the cell can no longer divide and it ages. In the end it dies.

How long the telomeres are is an indicator of the biological age of a cell. In addition to genetic factors, lifestyle factors such as stress or diet have a significant influence on telomere length.

In fact, it was found that precisely those participants whose immune cells had particularly long telomeres were more likely to be spared an infection.

Participants with short chromosome protective caps, on the other hand, were more likely to be infected. In particular, the teleomere length of certain T cells was crucial. These are responsible for detecting and eliminating infected body cells.
"Our work suggests that telomere length may be a relatively constant indicator of susceptibility to disease," explains study leader Cohen.

Greater influence in old age

Since the length of the cell telomeres naturally decreases with increasing age, it is not surprising that this factor also plays a role in susceptibility to infection. The length of the chromosome protective caps influenced the susceptibility of the older participants to infections more than that of the younger ones. In the group of 18 to 22 year olds, the telomere length has practically no influence on the risk of infection.

"It is understandable that the importance of telomere length increases with age. Because young participants have fewer cells with very short telomeres, the effect is not as pronounced," explains Cohen. However, a young immune system might be able to better compensate for the loss of effectively working cells.

However, it is not yet entirely certain that the short telomeres have a direct influence on the risk of disease. It is also conceivable that a previously unknown third factor influences both.

In other diseases, however, the role of telomeres is better documented. These include, for example, cancer. But the general risk of death is also associated with telomere length. (cf)

Source: Sheldon Cohen: Association Between Telomere Length and Experimentally Induced Upper Respiratory Viral Infection in Healthy Adults, JAMA. 2013; 309: 699-705. doi: 10.1001 / jama.2013.613

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