Smelling bone marrow transplants

I just recently wrote about a recent discovery that find people can smell without their noses (hint they use their skin) . Well, a new article by Lavi Secundo et. al. finds that the nose is still useful, since the olfactory receptors in a nose are so unique that they can distinguish humans from one another and this distinction can be used to find bone marrow transplant donors! [1]

Every person has about ~400 different olfactory receptor subtypes. The exact amount and kind of all receptors are probably unique for every person which implies that its likely that all people percieve smells slightly differently from one another. To test this, Lavi Secundo gave a bunch of people things to smell and asked them to rate the smell on a sliding scale about whether the smell was “masculine” or “lemony” or “edible”. After barging with smells, the researchers built up a matrix containing the smell profile of each person. Not surprisingly, the matrices were unique enough to easily identify people!

Whats amazing, is that the researchers took this one step beyond just telling people apart. Its been established that the olfactory receptor genome is linked to the immune system genes in mice. [2] The researchers hypothesized that maybe the olfactory genes are also linked to the human immune system - the Human Leukocyte Antigens (HLAs). HLA matching is a prerequisite for bone marrow or blood cord transplants and its very important to have methods to determine whether people are matches (that hopefully are not super intrusive). It turns out that the ability to percieve smells did help to find HLA matches - in fact, using a simple smell test could reduce the number of HLA tests needed by more than 30%!

The health industry should care, because anything that cuts the cost and time of matching potential bone marrow donors could be very competitive in a market where the main alternative is to draw blood. Also, you should care because you can now feel special that you smell a world that is totally unique to you!

The authors didn’t actually compare the genomes of different patients to check how similar a smell fingerprint is to a HLA genotype or a olfactory receptor genotype… so that’s one thing to do! Also there is a problem in that the sense of smell can change over time so the persistence of these types of tests would have to be validated for future uses.

References

1. Secundo, Lavi, et al. “Individual olfactory perception reveals meaningful nonolfactory genetic information.” Proceedings of the National Academy of Sciences (2015): 201424826.
2. Younger, Ruth M., et al. “Characterization of clustered MHC-linked olfactory receptor genes in human and mouse.” Genome research 11.4 (2001): 519-530.