Sweaty T-Shirts and Immunity

A corny question to ask a prospective mate might be: So...what is your zodiac sign? A better question could be: So, what's in your HLA? A few studies suggest that people tend to choose their mates based on MHC dissimilarity. A paper by Chaix et al. published in PLOS Genetics demonstrates that European American couples are really dissimilar when MHC loci are compared....way more different than what is expected by pure randomness. Although this selection could be a semi-counscious choice as stated by the following:

"In a less direct way, other studies have focused on odor preferences: in “sweaty T-shirts experiments”, in which females were asked to smell T-shirts worn by different males, it was shown that females significantly prefer the odor of T-shirts worn by MHC-dissimilar males, although such preference was not found among females taking the contraceptive pill. However, in another sweaty T-shirts experiment, in which males where chosen from a different ethnicity from the females and females were not aware of the nature of the smell (contrary to the two previous studies), females significantly preferred the odor of males having a small number of HLA alleles matching their paternal inherited alleles than the odor of males having fewer matches."

The authors also mention that this selection could be totally up to the egg to "choose" the right sperm cell....