The major histocompatibility complex and the chemosensory signalling of individuality in humans.

The chemosensory identity of mice and rats is determined partly by polymorphic genes of the major histocompatibility complex (MHC). In inbred strains of mice, as well as in seminatural populations, MHC-associated mating preferences selectively influence reproductive success, thus serving to promote heterozygocity in the MHC. In order to determine whether MHC-associated chemosignals are present in humans, two studies were conducted. In a first study, olfactory identification of MHC-associated chemosignals was conducted on 12 trained rats' responses to the urine odors of humans. In a second study, MHC-associated olfactory cues in humans were analyzed by means of gas chromatography. The results indicate that the urine odors of humans are associated with the MHC and demonstrate that the profile of volatile components in the urine odors shows some association with the MHC. Furthermore, results show that a profile of some specific components, as well as a few ubiquitous volatiles, constitutes MHC-associated odor signals in humans.

Molecular forms of soluble HLA in body fluids: potential determinants of body odor cues.

The major histocompatibility complex (MHC) has been linked to encoding for individual olfactory identity. Experiments in mice and rats proved that behavior and mating were, at least in part, determined by genes within the MHC. This study was aimed at investigating whether sHLA are excreted in human urine, saliva and sweat. In particular examination of the molecular forms in these fluids would give clues to whether break down forms of soluble MHC molecules might participate in shaping behavior. Major bands of 45, 40, and 23 kD were detectable. Increased levels of sHLA were measured using a quantitative ELISA in urine shortly before ovulation decreasing to normal levels thereafter. In animal models strain specific MHC-linked odor cues have been detected in urine. Thus, excretion of sHLA in urine might indicate a similar role for these molecules in humans.

Soluble MHC class I molecules in human body fluids.

Apart from their well-known function of antigen presentation in the form of peptides, major histocompatibility antigens (MHC) have been found to be unique markers of individual body odors in murine experimental models. In the current study we examined the nature and expression of soluble human MHC class I molecules in body fluids. Biochemical analysis of affinity purified serum class I molecules revealed a variety of molecules within the molecular weight region of 45 to 21 kD. SDS-Western blotting of HLA derived from hepatocytes and spleen cells suggested that much of the small molecular mass fraction of sHLA (< 45 kD) found in serum is derived from the liver. sHLA were detected and quantitated in serum, plasma, urine, cerebrospinal fluid, and sweat. No sHLA were detectable in cerebrospinal fluid (n = 20). In addition, sHLA was measured in serum of women during the menstrual cycle. A significant increase in sHLA was observed during the first half of the cycle, suggesting that sexual hormones may increase sHLA concentration. The observed increase was most prominent in women that were HLA-A24.