Soluble MHC class I molecules in human body fluids

Abstract

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.