{{Short description|Sex-specific cell surface antigen in mammals}} {{Infobox protein |Name=anti-Müllerian hormone |caption= |image= |width= |HGNCid=464 |Symbol=AMH |AltSymbols= |EntrezGene=268 |OMIM=600957 |RefSeq=NM_000479 |UniProt=P03971 |PDB= |ECnumber= |Chromosome=19 |Arm=p |Band=13.3 |LocusSupplementaryData= }} {{Infobox protein |Name=Lysine-Specific Demethylase 5D protein |caption= |image= |width= |HGNCid=11115 |Symbol= KDM5D |AltSymbols=HYA, SMCY |EntrezGene= |OMIM=426000 |RefSeq=NM_004653 |UniProt=Q9BY66 |PDB= |ECnumber= |Chromosome=Y |Arm=q |Band=11.223 |LocusSupplementaryData= }} {{Infobox protein |Name=Male Enhanced Antigen 1 |caption= |image= |width= |HGNCid=6986 |Symbol= MEA1 |AltSymbols=HYS |EntrezGene= |OMIM=143170 |RefSeq=NM_001318942 |UniProt=Q16626 |PDB= |ECnumber= |Chromosome=6 |Arm=p |Band=21.1 |LocusSupplementaryData= }} '''H-Y antigen''' is a male tissue specific antigen.<ref name="Müller" /> Originally thought to trigger the formation of testes (via loci, an autosomal gene that generates the antigen and one that generates the receptor)<ref>{{cite web|title=H-Y Antigen|url=http://www.medilexicon.com/medicaldictionary.php?t=4891|url-status=dead|archive-url=https://web.archive.org/web/20171130181202/http://www.medilexicon.com/dictionary/4891|archive-date=2017-11-30|work=mediLexicon|publisher=Wolters Kluwer}}</ref> it is now known that it does not trigger the formation of testes but may be activated by the formation of testes.<ref name="Wolf"/>

There are several antigens which qualify as H-Y as defined by rejection of male skin grafts in female hosts or detected by cytotoxic T cells or antibodies. One H-Y, secreted by the testis, defined by antibodies, is identical to Müllerian-inhibiting substance (AMH gene).<ref name="Müller" /> Another H-Y, minor histocompatibility antigen, seemed to be encoded in the SMCY gene (acronym for 'selected mouse cDNA on Y'), later identified as an 11-residue peptide from the Lysine-Specific Demethylase 5D protein (KDM5D gene) presented by HLA-B7. A third example is MEA1.

==Association with spermatogenesis== It has been shown that male mice lacking in the H-Y antigen, hence lacking in the gene producing it, have also lost genetic information responsible for spermatogenesis.<ref name="Burgoyne, Levy, McLaren"/> This result also identified a gene on the mouse Y chromosome, distinct from the testis-determining gene, that was essential for spermatogenesis, thus raising the possibility that the very product of this "spermatogenesis gene" is the H-Y antigen.<ref name="Burgoyne, Levy, McLaren"/>

==Male homosexuality and the birth order effect== Among humans, it has been observed that men with more older brothers tend to have a higher chance of being homosexual (see Fraternal birth order and male sexual orientation). For every additional older brother, a man's chance of being homosexual can rise by up to 33%.<ref name="Ridley, M 2000">{{cite book | vauthors = Ridley M | year = 2000 | title = Genome: The Autobiography of a Species in 23 Chapters. | publisher = Harper and Collins | isbn = 978-0-06-089408-5 }}</ref> One theory to explain this involves H-Y antigens, which suggests that a maternal immune reaction to these antigens has, to an extent, an inhibitory effect on the masculinization of the brain, and therefore, the more male foetuses that the mother of a man has had, the greater the maternal immune response towards him<ref>{{cite web | first = Tom | last = Dare | name-list-style = vanc | date = 8 October 2013 | url = https://www.youtube.com/watch?v=7dujRs7JDZ0 | title = Vaccination and immunity for iGCSE Biology | publisher = YouTube }}</ref> and thus the greater the inhibitory effect on brain masculinization, which is believed to be a factor in sexual orientation.<ref name="Ridley, M 2000"/>

This hypothesis is supported by evidence that older sisters have no discernible influence on the sexual orientation of later-born males, which would be expected since H-Y antigen is male tissue specific, the 'probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring'.<ref name="Blanchard, Klassen" /> More specifically, recent research (Jan 2018) has found maternal antibodies to the neuroligin NLGN4Y protein, a Y-chromosome protein important in male fetal brain development, to be involved in the fraternal birth order effect.<ref name="Bogaert Skorska Wang Gabrie 2018 p.">{{cite journal | vauthors = Bogaert AF, Skorska MN, Wang C, Gabrie J, MacNeil AJ, Hoffarth MR, VanderLaan DP, Zucker KJ, Blanchard R | title = Male homosexuality and maternal immune responsivity to the Y-linked protein NLGN4Y | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 115 | issue = 2 | pages = 302–306 | date = January 2018 | pmid = 29229842 | pmc = 5777026 | doi = 10.1073/pnas.1705895114 | bibcode = 2018PNAS..115..302B | doi-access = free }}</ref>

==References== <references>

<ref name="Müller">{{cite journal | vauthors = Müller U | title = H-Y antigens | journal = Human Genetics | volume = 97 | issue = 6 | pages = 701–4 | date = June 1996 | pmid = 8641682 | doi = 10.1007/BF02346175| s2cid = 25641671 }}</ref>

<ref name="Wolf">{{cite journal | vauthors = Wolf U | title = The serologically detected H-Y antigen revisited | journal = Cytogenetics and Cell Genetics | volume = 80 | issue = 1–4 | pages = 232–5 | date = 1998 | pmid = 9678364 | doi = 10.1159/000014986 | s2cid = 25908189 }}</ref>

<ref name="Blanchard, Klassen">{{cite journal | vauthors = Blanchard R, Klassen P | title = H-Y antigen and homosexuality in men | journal = Journal of Theoretical Biology | volume = 185 | issue = 3 | pages = 373–8 | date = April 1997 | pmid = 9156085 | doi = 10.1006/jtbi.1996.0315 | bibcode = 1997JThBi.185..373B | citeseerx = 10.1.1.602.8423 }}</ref>

<ref name="Burgoyne, Levy, McLaren">{{cite journal | vauthors = Burgoyne PS, Levy ER, McLaren A | title = Spermatogenic failure in male mice lacking H-Y antigen | journal = Nature | volume = 320 | issue = 6058 | pages = 170–2 | date = 1986 | pmid = 3951555 | doi = 10.1038/320170a0 | bibcode = 1986Natur.320..170B | s2cid = 4284719 }}</ref>

</references>

Category:Immune system Category:Male homosexuality