The immune system and mating behavior of vertebrates appear to be closely linked. In a now classically unpleasant experiment, female students not taking oral contraceptives were asked to rate the pleasantness of men’s sweaty T-shirts. I doubt that any of those T-shirts were emitting a pleasant odour, but some were rated higher than others and as it turned out, there was a correlation between MHC mismatch and a positive rating. From an evolutionary and adaption perspective, it may make sense. We want our offspring to have increased diversity in order to fight infection.


Snakes, birds and mice seem to discriminate between individuals based on odour. Pheasant females, for example, have been shown to choose males with MHC genotypes that confer disease resistance. In early 2000, two papers showed that pheromones detected by neurons of the mouse vomeronasal organ (VNO) located in the nasal septum relay chemical information to the regions of the hypothalamus associated with reproductive behavior. The papers also showed that certain neurons within the VNO express non-classical MHC molecules, M1 and M10, found in the H2 locus. More interesting was that M10 was exclusively expressed within the VNO in a complex together with b2-microglobulin and could respond to MHC Class I peptides. MHC-peptide binding was shown to be highly dependent on peptide anchor resides and VN receptors could discriminate peptides differing in one single amino acid. Although two VNO-equivalent gene clusters have been mapped near the HLA class I region, all other evidence has been inconsistent in humans.

It appears that the decision for mating partner in humans is based on a variety of factors such as facial symmetry, physique, skin condition, and perhaps even body odour. Funny enough, studies on facial symmetry showed contradictory results. When asked to judge the faces of males who were either MHC-similar or dissimilar, women preferred the former.

So perhaps our mating choices are not entirely based on smelling sweat and hoping that their MHC will be different from our own.




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Patrycja Thompson

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