{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T22:28:00Z","timestamp":1785536880863,"version":"3.56.0"},"reference-count":38,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2022,11,30]],"date-time":"2022-11-30T00:00:00Z","timestamp":1669766400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004281","name":"National Science Center","doi-asserted-by":"publisher","award":["NCN grant 2020\/36\/C\/NZ9\/00192"],"award-info":[{"award-number":["NCN grant 2020\/36\/C\/NZ9\/00192"]}],"id":[{"id":"10.13039\/501100004281","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Endometrial immune cells are essential to support uterine functions across the estrous cycle and in preparation for pregnancy. It has been acknowledged that changes in phenotype and\/or numbers of lymphocytes, such as regulatory T cells (Tregs) and NK cells, might result in lower fertility in women and mice. Little is known about equine endometrial immune cells across the estrous cycle. Here, we compared the populations of endometrial Tregs and NK cells in estrus and diestrus in mares. Endometrial biopsy and blood samples were taken in estrus and diestrus from 11 mares ages 4\u201312 years. Flow cytometry with anti-CD4, -CD25 and -FOXP3 and anti-NKp46 and -CD3 antibodies was used to determine the populations of Tregs and NK cells, respectively. The concentration of progesterone was measured with chemiluminescence immunoassay. The results were analyzed with paired Student t tests. The mean percentage of endometrial CD4+FOXP3+ Tregs was 13.7 \u00b1 6.2% in diestrus and 14.5 \u00b1 5.9% in estrus, while the mean percentage of endometrial CD4+FOXP3+CD25+ Tregs changed from 3.6 \u00b1 2.1% in diestrus to 2 \u00b1 2% in estrus (p = 0.0947). The mean proportion of CD3\u2212NKp46+ lymphocytes in the endometrium was not significantly different, with 6 \u00b1 1% in estrus and 6.5 \u00b1 1.4% in diestrus. There was a large variation in the percentage of NK cells between mares of 2.1\u201312.7%. This study showed, for the first time, the presence of CD4+FOXP3+CD25+ Tregs and CD3\u2212NKp46+ NK cells in the endometrium of non-pregnant cycling mares. The percentage of Tregs, and to a greater extent NK cells, showed large fluctuations between mares. Both Tregs and NK cells might be important for the preparation of the endometrium for semen deposition and pregnancy; however, further research is required.<\/jats:p>","DOI":"10.3390\/ani12233373","type":"journal-article","created":{"date-parts":[[2022,12,1]],"date-time":"2022-12-01T02:24:46Z","timestamp":1669861486000},"page":"3373","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Populations of NK Cells and Regulatory T Cells in the Endometrium of Cycling Mares\u2014A Preliminary Study"],"prefix":"10.3390","volume":"12","author":[{"given":"Joanna","family":"Jaworska","sequence":"first","affiliation":[{"name":"Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9422-2370","authenticated-orcid":false,"given":"Amanda M.","family":"de Mestre","sequence":"additional","affiliation":[{"name":"Department of Comparative Biomedical Sciences, Royal Veterinary College, Hertfordshire, Hatfield AL9 7TA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3284-1106","authenticated-orcid":false,"given":"Joanna","family":"Wi\u015bniewska","sequence":"additional","affiliation":[{"name":"Laboratory of Cell and Tissue Analysis and Imaging, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bettina","family":"Wagner","sequence":"additional","affiliation":[{"name":"Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8776-9490","authenticated-orcid":false,"given":"Arkadiusz","family":"Nowicki","sequence":"additional","affiliation":[{"name":"Private Veterinary Practice Arkadiusz Nowicki, 10-684 Olsztyn, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1176-5557","authenticated-orcid":false,"given":"Ilona","family":"Kowalczyk-Zi\u0119ba","sequence":"additional","affiliation":[{"name":"Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1270-3438","authenticated-orcid":false,"given":"Izabela","family":"Woc\u0142awek-Potocka","sequence":"additional","affiliation":[{"name":"Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, 10-747 Olsztyn, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"16","DOI":"10.4110\/in.2015.15.1.16","article-title":"Immune cells in the female reproductive tract","volume":"15","author":"Lee","year":"2015","journal-title":"Immune Netw."},{"key":"ref_2","first-page":"387","article-title":"Immunology of normal and abnormal menstruation","volume":"9","author":"Berbic","year":"2013","journal-title":"Womens Health"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"S26","DOI":"10.1016\/j.placenta.2008.09.019","article-title":"Comparison of immune cell recruitment and function in endometrium during development of epitheliochorial (pig) and hemochorial (mouse and human) placentas","volume":"30","author":"Croy","year":"2009","journal-title":"Placenta"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"434","DOI":"10.1111\/j.1600-0897.2009.00794.x","article-title":"The unique properties of uterine NK cells","volume":"63","author":"Manaster","year":"2010","journal-title":"Am. 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