MHC and mate choice: Happy Hallmark Day!

[jeskill]

I love this story and it was retold in my evolutionary ecology class today so I thought I'd bring it here for discussion. (Feel free to correct me if I get anything wrong).

 

MHC, the major histocompatibility complex in vertebrates (HLA in humans), is a group of many, highly variable genes involved in immune response to viruses, bacteria, parasites. More variability seems to be correlated with an increased resistance. Therefore, there is an advantage to mating with individuals whose MHC genes are different than yours.

 

Apparently, we can smell the MHC type of other individuals, hence one of the reasons why people have distinct odors. It's thought that this distinct odor is the result of an interaction between the "internal flora" (read Bacteria) and peptides associated with the MHCs.

 

As evidence, Claus Wedekind, a zoologist at Bern University in Switzerland performed the famous "T-shirt" study, where males wore the same shirt for a couple nights without bathing or putting on deodorant, then females smelled the shirts to determine who had the sexiest scent.

The results: Women consistently picked men with different MHC types than their own UNLESS they were one the pill, then they liked similar MHC types.

 

Second piece of evidence:

Manfred Milinski and Claus Wedekind published a study in 2001 that shows that people prefer to wear the perfume scent that matches their own MHC type, perhaps because it amplifies our MHC types and it could mask the smell of illness, make us smell healthier.

 

Now for the business idea:

What about starting an online business that uses molecular markers to determine an individual's MHC-type and then matching them with perfume that is designed to smell most similar to their MHC type? How much do you think it would cost per individual (not including start-up costs)?

 

Happy Happy.

[prion]

but has anyone actually correlated MHC/HLA with odour? I understood it was just speculation: i.e. from the discovery that people on average tend to choose the scent of people with different HLA to them, it was speculated that HLA might somehow influence the way you smell? Association doesn't prove causation, I mean if unrelated people smell different because of some other genetic effect on odour, you'd still get the same result in the T-shirt experiment.

[rakuenso]

see that would be the case if humans were animals in the state of nature...

 

I've read about the t-shirt experiment, but it's only valid when the females are provided ONLY T-shirts to smell. In real life, i think females receive alot more than smelly t-shirts.

[jeskill]

In animals with the vomeronasal (pheromone) organ still intact, MHC molecules are functionally associated with one of the pheromone receptor families (V2R). - see Dulac and Torello (2003) in Nature Reviews 4:551

 

You are right that association doesn't prove causation, but studies on mice MHCs have shown this phenomenon too. Of course, we don't have working pheromone receptors, so the question becomes, how are we sensing pheromone-like odours, if we indeed are sensing them (i.e. odours that cause behavioural or physiological changes)?

 

What else do you think it could be?

 

but has anyone actually correlated MHC/HLA with odour? I understood it was just speculation: i.e. from the discovery that people on average tend to choose the scent of people with different HLA to them, it was speculated that HLA might somehow influence the way you smell? Association doesn't prove causation, I mean if unrelated people smell different because of some other genetic effect on odour, you'd still get the same result in the T-shirt experiment.

[prion]

Interesting, I didn't realise it had been studied in detail at the molecular level. There still seem to be a lot of unanswered questions though. It reminds me of the issue of light affecting circadian rhythm - when people knew for ages that certain wavelengths of light affected sleep/wake cycles but just couldn't think how, then eventually they found a whole new photoreceptor in the eye. Maybe something similar will happen with this area