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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="brief-report" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Russian Journal of Immunology</journal-id><journal-title-group><journal-title xml:lang="en">Russian Journal of Immunology</journal-title><trans-title-group xml:lang="ru"><trans-title>Российский иммунологический журнал</trans-title></trans-title-group></journal-title-group><issn publication-format="print">1028-7221</issn><issn publication-format="electronic">2782-7291</issn><publisher><publisher-name xml:lang="en">Russian Society of Immunology</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">17158</article-id><article-id pub-id-type="doi">10.46235/1028-7221-17158-PCO</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>SHORT COMMUNICATIONS</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>КРАТКИЕ СООБЩЕНИЯ</subject></subj-group><subj-group subj-group-type="article-type"><subject>Short Communication</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Phenotypic characteristics of double-positive T cells in peripheral blood of healthy adults</article-title><trans-title-group xml:lang="ru"><trans-title>Фенотипическая характеристика дважды позитивных Т-клеток в периферической крови условно здоровых доноров</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><name-alternatives><name xml:lang="en"><surname>Rubinstein</surname><given-names>Artem A.</given-names></name><name xml:lang="ru"><surname>Рубинштейн</surname><given-names>Артем Аркадьевич</given-names></name></name-alternatives><address><country country="RU">Russian Federation</country></address><bio xml:lang="en"><p>General Practitioner, Junior Researcher, Department of Cellular Immunology</p></bio><bio xml:lang="ru"><p>врач общей практики, младший научный сотрудник лаборатории клеточной иммунологии</p></bio><email>arrubin6@mail.ru</email><xref ref-type="aff" rid="aff1"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">Institute of Experimental Medicine</institution></aff><aff><institution xml:lang="ru">ФГБНУ «Институт экспериментальной медицины»</institution></aff></aff-alternatives><pub-date date-type="preprint" iso-8601-date="2025-07-09" publication-format="electronic"><day>09</day><month>07</month><year>2025</year></pub-date><pub-date date-type="pub" iso-8601-date="2025-09-18" publication-format="electronic"><day>18</day><month>09</month><year>2025</year></pub-date><volume>28</volume><issue>3</issue><issue-title xml:lang="en"/><issue-title xml:lang="ru"/><fpage>579</fpage><lpage>584</lpage><history><date date-type="received" iso-8601-date="2025-03-28"><day>28</day><month>03</month><year>2025</year></date><date date-type="accepted" iso-8601-date="2025-05-25"><day>25</day><month>05</month><year>2025</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2025, Rubinstein A.A.</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2025, Рубинштейн А.А.</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="en">Rubinstein A.A.</copyright-holder><copyright-holder xml:lang="ru">Рубинштейн А.А.</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/"/><license><ali:license_ref xmlns:ali="http://www.niso.org/schemas/ali/1.0/">https://creativecommons.org/licenses/by/4.0</ali:license_ref></license></permissions><self-uri xlink:href="https://rusimmun.ru/jour/article/view/17158">https://rusimmun.ru/jour/article/view/17158</self-uri><abstract xml:lang="en"><p>Recent studies have shown that healthy adults have circulating double-positive (DP) T cells at small concentrations. These T cells develop from CD4<sup>+</sup> and CD8<sup>+</sup>T cell populations and co-express CD4 and CD8 on their surface. According to the expression of CD4 and CD8 markers, the DP T cells can be divided into two subpopulations: CD4<sup>bright</sup>CD8<sup>dim</sup> and CD4<sup>dim</sup>CD8<sup>bright</sup>. The phenotypic and functional features of these subpopulations are currently not fully understood. The aim of the study was to identify the phenotypic characteristics of CD4<sup>bright</sup>CD8<sup>dim</sup> and CD4<sup>dim</sup>CD8<sup>bright</sup>T cells in peripheral blood from healthy adults depending on the expression of maturation antigens. The cell phenotyping was performed by flow cytometry using antibodies against the following human surface antigens: CD57 (FITC-conjugated), CD62L (ECD-conjugated), CD28 (PerCP/Cy5.5-conjugated), CD27 (Pe/Cy7-conjugated), CD4 (APC-conjugated), CD8 (APC-AF700-conjugated), CD3 (APC-AF750-conjugated), CD45RA (Pacific Blue-conjugated), and CD45 (Krome Orange-conjugated). The differences between the groups were estimated using Mann–Whitney U test. Results were presented as median and interquartile range – Me (Q<sub>0.25</sub>-Q<sub>0.75</sub>). A total pool of DP T cells was detected, constituting 0.73% (0.42-1.61) of the total CD3<sup>+</sup>T cell population, at a total concentration of 11 cells/μL (6-20). The percentage of CD4<sup>bright</sup>CD8<sup>dim</sup> and CD4<sup>dim</sup>CD8<sup>bright</sup>T cells was within 0.25% (0.18-0.44), and 0.29% (0.20-0.98) at concentrations of 4 cells/1μL (2-7) and 5 cells/1μL (2-12), respectively. Effector memory cells (CD45RA<sup>-</sup>CD62L<sup>-</sup>) and effector memory cells re-expressing CD45RA (CD45RA<sup>+</sup>CD62L<sup>-</sup>) were predominant in CD4<sup>bright</sup>CD8<sup>dim</sup> T cells, whereas central memory phenotype (CD45RA<sup>+</sup>CD62L<sup>+</sup>) prevailed among CD4<sup>dim</sup>CD8<sup>bright</sup>T cells. Moreover, a reduced level of the “naïve” phenotype (CD45RA<sup>+</sup>CD62L<sup>+</sup>) was noted in CD4<sup>bright</sup>CD8<sup>dim</sup> and CD4<sup>dim</sup>CD8<sup>bright</sup>T cell populations. An increase in CD57 expression on the surface of CD4<sup>bright</sup>CD8<sup>dim</sup>T cells with a simultaneous decrease in CD27 and CD28 was also detected as compared to CD4<sup>+</sup>T cells. In turn, CD4<sup>dim</sup>CD8<sup>bright</sup>T cells increase the expression of CD28 and decrease the expression of CD57 on their surface if compared to CD8<sup>+</sup>T cells. DP T cells have a more mature phenotype being often represented by memory cells.</p></abstract><trans-abstract xml:lang="ru"><p>Исследования последних лет показали, что у здоровых людей при физиологической норме могут циркулировать дважды позитивные (DP) Т-клетки в небольшом количестве. Эти Т-лимфоциты происходят от циркулирующих CD4<sup>+</sup> и CD8<sup>+</sup>Т-лимфоцитов, но отличаются коэкспрессией CD4 и CD8 на своей поверхности. По выраженности экспрессии CD4 и CD8, DP Т-лимфоциты можно подразделить на две субпопуляции: CD4<sup>bright</sup>CD8<sup>dim</sup> и CD4<sup>dim</sup>CD8<sup>bright</sup>. Фенотипические и функциональные особенности этих субпопуляций в настоящее время до конца не изучены. Цель исследования – выявить фенотипические характеристики CD4<sup>bright</sup>CD8<sup>dim</sup> и CD4<sup>dim</sup>CD8<sup>bright</sup>Т-лимфоцитов периферической крови условно здоровых доноров в зависимости от экспрессии маркеров созревания. Фенотипирование проводилось при помощи проточной цитометрии с использованием антител против поверхностных антигенов человека: CD57 (конъюгирован с FITC), CD62L (конъюгирован с ECD), CD28 (конъюгирован с PerCP/Cy5.5), CD27 (конъюгирован с Pe/Cy7), CD4 (конъюгирован с APC), CD8 (конъюгирован с APC-AF700), CD3 (конъюгирован с APC-AF750), CD45RA (конъюгирован с Pacific Blue) и CD45 (конъюгирован с Krome Orange). Сравнение производилось при помощи непараметрического U-критерия Манна–Уитни. Результаты приводились в виде медианы и интерквартильного размаха – Me (Q<sub>0,25</sub>-Q<sub>0,75</sub>). Общий пул DP Т-клеток составляет в рамках общей популяции CD3<sup>+</sup>Т-лимфоцитов 0,73% (0,42-1,61) при общей концентрации 11 кл/1μL (6-20). Процентное содержание CD4<sup>bright</sup>CD8<sup>dim</sup> и CD4<sup>dim</sup>CD8<sup>bright</sup>T-клеток находилось в пределах 0,25% (0,18-0,44) и 0,29% (0,20-0,98) при концентрациях 4 кл/1μL (2-7) и 5 кл/1μL (2-12) соответственно. В Т-лимфоцитах с фенотипом CD4<sup>bright</sup>CD8<sup>dim</sup> преобладали клетки эффекторной памяти (CD45RA<sup>-</sup>CD62L<sup>-</sup>) и эффекторные клетки памяти, повторно экспрессирующие CD45RA (CD45RA<sup>+</sup>CD62L<sup>-</sup>), тогда как в CD4<sup>dim</sup>CD8<sup>bright</sup>T-клетках преобладал фенотип центральной памяти (CD45RA<sup>-</sup>CD62L<sup>+</sup>). Кроме того, в популяциях CD4<sup>bright</sup>CD8<sup>dim</sup> и CD4<sup>dim</sup>CD8<sup>bright</sup>T-клеток был отмечен пониженный уровень «наивного» фенотипа (CD45RA<sup>+</sup>CD62L<sup>+</sup>). Также было выявлено повышение экспрессии CD57 на поверхности CD4<sup>bright</sup>CD8<sup>dim</sup> Т-лимфоцитов с одновременным снижением CD27 и CD28 по сравнению с CD4<sup>+</sup>Т-клетками. В свою очередь, CD4<sup>dim</sup>CD8<sup>bright</sup>T-клетки увеличивают экспрессию CD28 и уменьшают экспрессию CD57 на своей поверхности по сравнению с CD8<sup>+</sup>Т-клетками. DP Т-лимфоциты обладают более зрелым фенотипом и зачастую представляют собой клетки памяти.</p></trans-abstract><kwd-group xml:lang="en"><kwd>flow cytometry</kwd><kwd>CD4+CD8+ T cells</kwd><kwd>double-positive T cells</kwd><kwd>T cell maturation</kwd><kwd>T cell differentiation</kwd><kwd>memory T cells.</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>проточная цитометрия</kwd><kwd>CD4+CD8+Т-клетки</kwd><kwd>дважды позитивные Т-клетки</kwd><kwd>созревание Т-клеток</kwd><kwd>дифференцировка Т-клеток</kwd><kwd>Т-клетки памяти</kwd></kwd-group><funding-group><award-group><funding-source><institution-wrap><institution xml:lang="ru">Министерства науки и высшего образования РФ</institution></institution-wrap><institution-wrap><institution xml:lang="en">Ministry of Science and Higher Education of the Russian Federation</institution></institution-wrap></funding-source><award-id>1022041101001-1</award-id></award-group></funding-group></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><mixed-citation>Alam M.R., Akinyemi A.O., Wang J., Howlader M., Farahani M.E., Nur M., Zhang M., Gu L., Li Z. 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