Sensory neurons with MHC-like peptide binding properties: disease consequences.

The recent discovery of specialized sensory neurons that bind peptides in an MHC-like fashion has revealed the long-sought odorants used to recognize the MHC genotype and phenotype of other individuals. The odorants are the same MHC peptides used during immune recognition, which provides the molecular logic linking selection acting on MHC-mediated behaviors with selection acting on immune recognition; both processes influence the evolving peptide binding properties of MHC molecules. The primary function of these chemosensory mechanisms for detecting MHC-mediated odors appears to be mating preferences (observed in humans and many vertebrates) that preferentially produce offspring more resistant to both infectious and genetic disease. Recent experiments are beginning to discriminate the relative importance of these different disease-reducing mechanisms.