Allogeneic recombinant soluble MHC class I molecules modify urinary odor cues in rats

The highly polymorphic genes of the major histocompatibility complex (MHC) determine, in part, the odor cues and behavior of an individual. In animal models, MHC-associated odors that regulate distinct behavior have been iden tified mainly in urine. However, the underlying mechanism is still not clea r. Here, we show that injected recombinant soluble (rs) MHC class I molecul es (DA, rsRT1.A(a) and Lewis, rsRT1.A(1)) temporarily alter urine odor of L ewis test rats (RTI.A(1)). This change in urinary signals was observed in b ehavioral assays using the habituation/dishabituation test and in odor sign als analysed by gas chromatography (GC) and mass spectrometry (MS). Gas chr omatographic analysis revealed that these altered odor signals are caused b y quantitative changes of at least two nitrogen-containing urinary compound s. The results suggest that urinary olfactory cues are directly or indirect ly influenced by MHC class I gene products. (C) 2001 Elsevier Science Inc. All rights reserved.