Body odour preferences in men and women: do they aim for specific MHC combinations or simply heterozygosity?

Abstract

The major histocompatibility complex (MHC) is an immunologically important group of genes that appears to be under natural as well as sexual selection. Several hypotheses suggest that certain MHC-allele combinations (usually heterozygous ones) are superior under selective pressure by pathogens. This could influence mate choice in a way that preferences function to create MHC-heterozygous offspring, or that they function to create specific allele combinations that are beneficial under the current environmental conditions through their complementary or epistatic effects. To test these hypotheses, we asked 121 men and women to score the odours of six T-shirts, worn by two women and four men. Their scorings of pleasantness correlated negatively with the degree of MHC similarity between smeller and T-shirt-wearer in men and women who were not using the contraceptive pill (but not in Pill-users). Depending on the T-shirt-wearer, the amount of variance in the scorings of odour pleasantness that was explained by the degree of MHC similarity (r2) varied between nearly 0 and 23%. There was no apparent effect of gender in this correlation: the highest r2 was actually reached with one of the male odours sniffed by male smellers. Men and women who were reminded of their own mate/ex-mate when sniffing a T-shirt had significantly fewer MHC-alleles in common with this T-shirt-wearer than expected by chance. This suggests that the MHC or linked genes influence human mate choice. We found no significant effect when we tested for an influence of the MHC on odour preferences after the degree of similarity between T-shirt-wearer and smeller was statistically controlled for. This suggests that in our study populations the MHC influences body odour preferences mainly, if not exclusively, by the degree of similarity or dissimilarity. The observed preferences would increase heterozygosity in the progeny. They do not seem to aim for more specific MHC combinations.

Genome-wide association analysis on five isolated populations identifies variants of the HLA-DOA gene associated with white wine liking

“…Women have in fact been described as being more sensitive than men to specific odors 52,53 also in the specific case of MHC driven body odor recognition. 54,55 The precise mechanism of how MHC class II molecules actually interact with the olfactory epithelium and how the signal is then transferred to the brain is still unknown and further studies are needed to clarify this point.…”

“…Women have in fact been described as being more sensitive than men to specific odors 52,53 also in the specific case of MHC driven body odor recognition. 54,55 The precise mechanism of how MHC class II molecules actually interact with the olfactory epithelium and how the signal is then transferred to the brain is still unknown and further studies are needed to clarify this point.We have previously reported rs4920566 (NC_000001.11: g.18853330 A4G) in the TAS1R2 gene as being associated to white wine liking. Checking in the results from the combined meta-analysis, this SNP resulted to be non significant (P-value = 0.83).…”

Increased heterozygosity for MHC class II lineages in newborn males

“…66,67 By offering genetically diverse rather than uniform sperms, heterozygote males would increase their chances in sperm selection (selective fertilization), in selective implantation and embryonic growth. If the pre-copulatory mate choice concerns the MHC and aims for heterozygosity as several studies suggested, 61,63,68 heterozygote males will have advantage over homozygotes. In male pheasants, there is a correlation between their MHC types and spur length which is a sexually selected trait.…”

An Evolutionary Approach Offers a Fresh Perspective on the Relationship Between Oral Contraception and Sexual Desire

“…Humans, too, can discriminate MHC similarity through odor: in laboratory tests, women in the follicular phase tend to rate axillary odor of MHC-dissimilar men as more sexy and attractive than those of MHC-similar men (Havlicek & Roberts, 2009;Wedekind & Füri, 1997;Wedekind, Seebeck, Bettens, & Paepke, 1995). Differences in preference for MHC dissimilarity also occur between OC users and non-users, with users showing weaker preference (Havlicek & Roberts, 2009;Wedekind & Füri, 1997;Wedekind et al, 1995).…”