{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,24]],"date-time":"2026-10-24T01:23:04Z","timestamp":1792804984389,"version":"4.5.0"},"reference-count":72,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2026,5,17]],"date-time":"2026-05-17T00:00:00Z","timestamp":1778976000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Medical University\u2013Plovdiv","award":["BG-RRP-2.004-0007-C01"],"award-info":[{"award-number":["BG-RRP-2.004-0007-C01"]}],"id":[{"id":"https:\/\/ror.org\/02kzxd152","id-type":"ROR","asserted-by":"crossref"}]},{"award":["BG-RRP-2.004-0007-C01"],"award-info":[{"award-number":["BG-RRP-2.004-0007-C01"]}],"id":[{"id":"https:\/\/ror.org\/02kzxd152","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Myalgic encephalomyelitis\/chronic fatigue syndrome (ME\/CFS) and long Coronavirus Disease 2019 (long COVID) are complex chronic conditions that often follow infectious triggers with overlapping clinical features but poorly defined pathophysiological relationships. This study aimed to identify disease-specific immune signatures through multiparameter immunophenotyping of monocytes, dendritic cells, and T cell subsets. A total of 207 participants were included (ME\/CFS: n = 103; long COVID: n = 63; healthy controls: n = 41). Peripheral blood mononuclear cells were analyzed using multiparameter flow cytometry. Statistical analyses included non-parametric testing, age-adjusted Analysis of covariance (ANCOVA), correlation network analysis, and principal component analysis (PCA). Long COVID was characterized by increased M2-like monocyte polarization, elevated CD80 expression across monocyte subsets, expansion of dendritic cells, and reduced expression of activation markers, indicating persistent immune activation with features of immune exhaustion. In contrast, ME\/CFS exhibited reduced costimulatory molecule expression, impaired C-C chemokine receptor type 7 (CCR7)-mediated immune cell trafficking, and less coordinated activation patterns, consistent with a state of immune suppression. Correlation network analysis revealed more extensive and integrated immune interactions in long COVID, while PCA identified distinct immunophenotypic components and enabled moderate discrimination between the two conditions. These findings demonstrate that ME\/CFS and long COVID are characterized by distinct immune profiles, supporting the concept of divergent immunopathological mechanisms. The identified signatures may contribute to biomarker development and guide targeted therapeutic approaches.<\/jats:p>","DOI":"10.3390\/ijms27104488","type":"journal-article","created":{"date-parts":[[2026,5,18]],"date-time":"2026-05-18T14:40:31Z","timestamp":1779115231000},"page":"4488","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Comprehensive Immunophenotyping of Monocytes and Dendritic Cells Suggests Distinct Pathophysiology in Chronic Fatigue Syndrome and Long COVID"],"prefix":"10.3390","volume":"27","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0522-5682","authenticated-orcid":false,"given":"Steliyan","family":"Petrov","sequence":"first","affiliation":[{"name":"Department of Medical Microbiology and Immunology \u201cProf. Dr. Elissay Yanev\u201d, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4230-3299","authenticated-orcid":false,"given":"Martina","family":"Bozhkova","sequence":"additional","affiliation":[{"name":"Department of Medical Microbiology and Immunology \u201cProf. Dr. Elissay Yanev\u201d, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"},{"name":"Research Institute, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9028-2192","authenticated-orcid":false,"given":"Mariya","family":"Ivanovska","sequence":"additional","affiliation":[{"name":"Department of Medical Microbiology and Immunology \u201cProf. Dr. Elissay Yanev\u201d, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"},{"name":"Research Institute, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6395-4109","authenticated-orcid":false,"given":"Teodora","family":"Kalfova","sequence":"additional","affiliation":[{"name":"Department of Medical Microbiology and Immunology \u201cProf. Dr. Elissay Yanev\u201d, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dobrina","family":"Dudova","sequence":"additional","affiliation":[{"name":"Department of Medical Microbiology and Immunology \u201cProf. Dr. Elissay Yanev\u201d, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4708-6887","authenticated-orcid":false,"given":"Yana","family":"Todorova","sequence":"additional","affiliation":[{"name":"National Reference Laboratory of Immunology, National Center of Infectious and Parasitic Diseases (NCIPD), 1504 Sofia, Bulgaria"},{"name":"Research and Innovation Program for the Development of MU-PLOVDIV (SRIPD-MUP), Creation of a Network of Research Higher Schools, National Plan for Recovery and Sustainability, EuropeanUnion\u2013NextGenerationEU, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Radostina","family":"Dimitrova","sequence":"additional","affiliation":[{"name":"National Reference Laboratory of Immunology, National Center of Infectious and Parasitic Diseases (NCIPD), 1504 Sofia, Bulgaria"},{"name":"Research and Innovation Program for the Development of MU-PLOVDIV (SRIPD-MUP), Creation of a Network of Research Higher Schools, National Plan for Recovery and Sustainability, EuropeanUnion\u2013NextGenerationEU, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1357-6717","authenticated-orcid":false,"given":"Marianna","family":"Murdjeva","sequence":"additional","affiliation":[{"name":"Department of Microbiology and Virology, Medical University of Pleven, 5800 Pleven, Bulgaria"},{"name":"Institute of Innovation and Smart Technology, University of Telecommunication and Posts, 1700 Sofia, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7818-7587","authenticated-orcid":false,"given":"Hristo","family":"Taskov","sequence":"additional","affiliation":[{"name":"Research and Innovation Program for the Development of MU-PLOVDIV (SRIPD-MUP), Creation of a Network of Research Higher Schools, National Plan for Recovery and Sustainability, EuropeanUnion\u2013NextGenerationEU, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria","family":"Nikolova","sequence":"additional","affiliation":[{"name":"National Reference Laboratory of Immunology, National Center of Infectious and Parasitic Diseases (NCIPD), 1504 Sofia, Bulgaria"},{"name":"Research and Innovation Program for the Development of MU-PLOVDIV (SRIPD-MUP), Creation of a Network of Research Higher Schools, National Plan for Recovery and Sustainability, EuropeanUnion\u2013NextGenerationEU, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Maes","sequence":"additional","affiliation":[{"name":"Research and Innovation Program for the Development of MU-PLOVDIV (SRIPD-MUP), Creation of a Network of Research Higher Schools, National Plan for Recovery and Sustainability, EuropeanUnion\u2013NextGenerationEU, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"},{"name":"Sichuan Provincial Center for Mental Health, Sichuan Provincial People\u2019s Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu 610072, China"},{"name":"Key Laboratory of Psychosomatic Medicine, Chinese Academy of Medical Sciences, Chengdu 610072, China"},{"name":"Department of Psychiatry, Medical University of Plovdiv, 4002 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,5,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Novak, P., Systrom, D.M., Witte, A., Marciano, S.P., Felsenstein, D., Milunsky, J.M., Milunsky, A., Krier, J., and Fishman, M.C. 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