A Soluble Isoform of the Rhesus Monkey Nonclassical MHC Class I Molecule Mamu-AG Is Expressed in the Placenta and the Testis

• Published in: The Journal of immunology (1950) Vol. 169; no. 2; pp. 673 - 683
• Main Authors: Ryan, Andy F, Grendell, Richard L, Geraghty, Daniel E, Golos, Thaddeus G
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.07.2002
• Subjects: Amino Acid Sequence; Animals; Antibodies, Monoclonal - metabolism; Antigen-Antibody Reactions; Base Sequence; Blotting, Western; Female; Histocompatibility Antigens Class I - biosynthesis; Histocompatibility Antigens Class I - genetics; Histocompatibility Antigens Class I - immunology; HLA Antigens - biosynthesis; HLA Antigens - genetics; HLA-G Antigens; Humans; Immunohistochemistry; In Situ Hybridization; Macaca mulatta; Male; Molecular Sequence Data; Organ Specificity - genetics; Organ Specificity - immunology; Placenta - immunology; Placenta - metabolism; Protein Isoforms - biosynthesis; Protein Isoforms - genetics; Protein Isoforms - immunology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - biosynthesis; Sequence Homology, Nucleic Acid; Solubility; Staining and Labeling; Testis - immunology; Testis - metabolism; Transcription, Genetic - immunology
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.169.2.673

The nonclassical MHC class I locus HLA-G is expressed primarily in the placenta, although other sites of expression have been noted in normal and pathological situations. In addition, soluble HLA-G isoforms have been detected in the serum of pregnant and nonpregnant women as well as men. The rhesus monkey placenta expresses a novel nonclassical MHC class I molecule Mamu-AG, which has features remarkably similar to those of HLA-G. We determined that the rhesus placenta expresses Mamu-AG mRNA (Mamu-AG5), retaining intron 4 as previously noted in HLA-G5. Immunostaining experiments with Ab 16G1 against the soluble HLA-G5 intron 4 peptide demonstrated that an immunoreactive protein(s) was present in the syncytiotrophoblasts of the chorionic villi of the rhesus placenta, within villous cytotrophoblasts, and occasionally within cells of the villous stroma. The Mamu-AG5 mRNA was readily detected in rhesus testis (although not in ejaculated sperm). Whereas an Ab against membrane-bound Mamu-AG stained few cells, primarily in the interstitium of the testis, there was consistent immunostaining for Mamu-AG5 in cells within the seminiferous tubules, which was corroborated by localization of Mamu-AG mRNA by in situ hybridization. While primary spermatocytes were negative, Sertoli cells, spermatocytes, and spermatids were consistently positive for 16G1 immunostaining. The specific recognition of the soluble Mamu-AG isoform was confirmed by Western blotting of Mamu-AG5 expressed in heterologous cells. The results demonstrate that a soluble nonclassical MHC class I molecule is expressed in the rhesus monkey placenta and testis, and confirm and extend the unique homology between HLA-G and the rhesus nonclassical molecule Mamu-AG.