{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,18]],"date-time":"2026-10-18T02:59:43Z","timestamp":1792292383169,"version":"4.4.0"},"reference-count":51,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2025,5,25]],"date-time":"2025-05-25T00:00:00Z","timestamp":1748131200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Veterinary Sciences"],"abstract":"<jats:p>The spleen plays a critical role in the immune and hematopoietic systems of teleost fish, functioning as a major secondary lymphoid organ. This study provides a detailed morphological and ultrastructural assessment of the spleen in goldfish (Carassius auratus), focusing on its immunological organization and cellular diversity. Through light and transmission electron microscopy, we examined red and white pulps, identifying key features such as melanomacrophage centers (MMCs), ellipsoids, and various immune cell types. The red pulp was rich in sinusoidal capillaries and splenic cords, whereas the white pulp housed lymphocytes, dendritic cells, macrophages, and telocytes, all contributing to immune regulation. Notably, ellipsoids were surrounded by reticular and macrophage sheaths, forming a filtration barrier against pathogens. Ultrastructural analysis revealed diverse immune cells with active morphological traits, including macrophages with pseudopodia and pigment granules, dendritic cells with dendrite-like extensions, and epithelial reticular cells involved in forming the blood\u2013spleen barrier. These findings highlight the complex immunological microarchitecture of the goldfish spleen and its functional relevance in teleost immune responses.<\/jats:p>","DOI":"10.3390\/vetsci12060517","type":"journal-article","created":{"date-parts":[[2025,5,25]],"date-time":"2025-05-25T20:26:50Z","timestamp":1748204810000},"page":"517","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Morphological and Ultrastructural Insights into the Goldfish (Carassius auratus) Spleen: Immune Organization and Cellular Composition"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7975-3926","authenticated-orcid":false,"given":"Doaa M.","family":"Mokhtar","sequence":"first","affiliation":[{"name":"Department of Cell and Tissues, Faculty of Veterinary Medicine, Assiut University, Assiut 71526, Egypt"},{"name":"Department of Anatomy and Histology, School of Veterinary Medicine, Badr University in Assiut, Assiut 19952, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3008-4308","authenticated-orcid":false,"given":"Giacomo","family":"Zaccone","sequence":"additional","affiliation":[{"name":"Department of Veterinary Sciences, University of Messina, 98168 Messina, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2801-6066","authenticated-orcid":false,"given":"Manal T.","family":"Hussein","sequence":"additional","affiliation":[{"name":"Department of Cell and Tissues, Faculty of Veterinary Medicine, Assiut University, Assiut 71526, Egypt"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1007\/BF02002607","article-title":"The fish spleen: Structure and function","volume":"41","author":"Nilsson","year":"1985","journal-title":"Experientia"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Zapata, A.G. (2022). Lympho-Hematopoietic Microenvironments and Fish Immune System. Biology, 11.","DOI":"10.3390\/biology11050747"},{"key":"ref_3","first-page":"399","article-title":"An overview of the structural and functional aspects of immune cells in teleosts","volume":"36","author":"Mokhtar","year":"2021","journal-title":"Histol. Histopathol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"486","DOI":"10.17221\/3294-VETMED","article-title":"Innate and adaptive immunity in teleost fish: A review","volume":"56","author":"Uribe","year":"2011","journal-title":"Vet. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"514","DOI":"10.1016\/j.fsi.2019.10.071","article-title":"Spleen Melanomacrophage centers response of Nile tilapia during Aeromanas hydrophila and Mycobacterium marinum infections","volume":"95","author":"Manrique","year":"2019","journal-title":"Fish Shellfish Immunol."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Steinel, N.C., and Bolnick, D.I. (2017). Melanomacrophage centers as a histological indicator of immune function in fish and other poikilotherms. Front. Immunol., 8.","DOI":"10.3389\/fimmu.2017.00827"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Sayed, R.K.A., Zaccone, G., Capillo, G., Albano, M., and Mokhtar, D.M. (2022). Structural and Functional Aspects of the Spleen in Molly Fish Poecilia sphenops (Valenciennes, 1846): Synergistic Interactions of Stem Cells, Neurons, and Immune Cells. Biology, 11.","DOI":"10.3390\/biology11050779"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e33196","DOI":"10.1371\/journal.pone.0033196","article-title":"Functional identification of dendritic cells in the teleost model, rainbow trout (Oncorhynchus mykiss)","volume":"7","author":"Bassity","year":"2012","journal-title":"PLoS ONE"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1007\/s00251-020-01196-0","article-title":"Anatomy of teleost fish immune structures and organs","volume":"73","author":"Koppang","year":"2021","journal-title":"Immunogenetics"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"469","DOI":"10.1007\/BF00318160","article-title":"Investigation of the structural and functional features of splenic ellipsoids in rainbow trout (Oncorhynchus mykiss)","volume":"279","author":"Espenes","year":"1995","journal-title":"Cell Tissue Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1016\/j.jcpa.2004.11.003","article-title":"Filter function and immune complex trapping in splenic ellipsoids","volume":"132","author":"Wien","year":"2005","journal-title":"J. Comp. Pathol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"9963","DOI":"10.1074\/jbc.M600631200","article-title":"A novel hematopoietic granulin induces proliferation of goldfish (Carassius auratus L.) macrophages","volume":"281","author":"Hanington","year":"2006","journal-title":"J. Biol. Chem."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Noga, E.J. (2010). Fish Disease: Diagnosis and Treatment, Wiley-Blackwell. [2nd ed.].","DOI":"10.1002\/9781118786758"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Austin, B., and Austin, D.A. (2016). Bacterial Fish Pathogens: Disease of Farmed and Wild Fish, Springer International Publishing. [6th ed.].","DOI":"10.1007\/978-3-319-32674-0"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"340","DOI":"10.1638\/2012-0151R1.1","article-title":"Repeated exposure of goldfish (Carassius auratus) to tricaine methanesulfonate (MS-222)","volume":"44","author":"Posner","year":"2013","journal-title":"J. Zoo Wildl. Med."},{"key":"ref_16","first-page":"137A","article-title":"A formaldehyde-glutaraldehyde fixative of high osmolarity for use in electron microscopy","volume":"27","author":"Karnovsky","year":"1965","journal-title":"Cell Biol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1083\/jcb.17.1.208","article-title":"The use of lead citrates at high pH as an electron-opaque stain in electron microscopy","volume":"17","author":"Reynolds","year":"1963","journal-title":"Cell Biol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"126","DOI":"10.1016\/j.fsi.2004.09.005","article-title":"Ontogeny of the immune system of fish","volume":"20","author":"Zapata","year":"2006","journal-title":"Fish Shellfish Immunol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"525","DOI":"10.3390\/biology4030525","article-title":"The Mucosal Immune System of Teleost Fish","volume":"12","author":"Salinas","year":"2015","journal-title":"Biology"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"79","DOI":"10.1006\/fsim.1994.1007","article-title":"Comparative Immune and enzyme histochemical phenotypes of lymphoid and nonlymphoid cells within the spleen of Atlantic salmon (Salmo salar L.)","volume":"4","author":"Press","year":"1994","journal-title":"Fish Shellfish Immunol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/j.imlet.2012.08.003","article-title":"Immune system and immune responses in fish and their role in comparative immunity study: A model for higher organisms","volume":"148","author":"Rauta","year":"2012","journal-title":"Immunol. Lett."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1006\/fsim.1998.0181","article-title":"The Morphology of the Immune System in Teleost Fishes","volume":"9","author":"Press","year":"1999","journal-title":"Fish Shellfish Immunol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"110","DOI":"10.1016\/j.tvjl.2015.01.013","article-title":"Identification and structural composition of the blood\u2013spleen barrier in chickens","volume":"204","author":"Zhang","year":"2015","journal-title":"Vet. J."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1079","DOI":"10.1002\/ar.20917","article-title":"Architecture of the blood-spleen barrier in the soft-shelled turtle, Pelodiseus sinensis","volume":"292","author":"Bao","year":"2009","journal-title":"Anat. Rec."},{"key":"ref_25","first-page":"44","article-title":"Location of blood-spleen barrier of Pelteobagrus vachelli by Trypan blue staining","volume":"17","author":"He","year":"2021","journal-title":"South China Fish. Sci."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1002\/jmor.1051790205","article-title":"Phagocytosis in the spleen of the sunfish Lepomis spp","volume":"179","author":"Fulop","year":"1984","journal-title":"J. Morphol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"411","DOI":"10.1086\/695327","article-title":"The phylogony of the spleen","volume":"92","author":"Udroiu","year":"2017","journal-title":"Q. Rev. Biol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1111\/j.1365-2761.1978.tb00023.x","article-title":"Changes in the spleen of the channel catfish Ictalurus punetatus Rafinesque induced by infection with Aeromonas hydrophila","volume":"1","author":"Bach","year":"1978","journal-title":"J. Fish. Disease"},{"key":"ref_29","first-page":"47","article-title":"Uptake of bacterial antigens in the spleen of carp (Cyprinus carpio L.)","volume":"2","author":"Maas","year":"1982","journal-title":"Dev. Comp. Immunol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1219","DOI":"10.1046\/j.1444-2906.2002.00558.x","article-title":"Entrapment and transport of foreign material in the spleen and kidney of Japanese conger Conger myriaster","volume":"68","author":"Furukawa","year":"2002","journal-title":"Fish. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"566","DOI":"10.1016\/j.fsi.2019.09.050","article-title":"Characterization of the fish ovarian stroma during the spawning season: Cytochemical, immunohistochemical and ultrastructural studies","volume":"94","author":"Mokhtar","year":"2019","journal-title":"Fish Shellfish Immunol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"499","DOI":"10.1046\/j.1365-2761.2003.00485.x","article-title":"Melano-macrophage centers and their role in fish pathology","volume":"26","author":"Agius","year":"2003","journal-title":"J. Fish. Dis."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/j.dci.2014.10.003","article-title":"Isolation and cytochemical characterization of melanomacrophages and melanomacrophage clusters from goldfish (Carassius auratus L.)","volume":"48","author":"Magor","year":"2015","journal-title":"Dev. Comp. Immunol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1001","DOI":"10.1111\/jai.12445","article-title":"Response of splenic melanomacrophage centers of Oreochromis niloticus (Linnaeus, 1758) to inflammatory stimuli by BCG and foreign bodies","volume":"30","author":"Manrique","year":"2014","journal-title":"J. Appl. Ichthyol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"939","DOI":"10.1590\/S1516-35982011000500001","article-title":"True and apparent digestibility of protein and amino acids of feed in Nile tilapia","volume":"40","author":"Ribeiro","year":"2011","journal-title":"Rev. Bras. Zootec."},{"key":"ref_36","unstructured":"King, R., Beso, A.J.G., Candelaria, V.Y., Dela Cruz, J.G., Margie, S., Tameta, A.D.C., and Espinosa, A.A. (2016). Effects of Unleaded Petroleum on the Macrophage Aggregates (MA) formation in Red King tilapia (Oreochromis sp.) Fingerlings. bioRxiv, 044537."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/0959-8030(92)90058-6","article-title":"Piscine macrophage aggregates: A review","volume":"2","author":"Wolke","year":"1992","journal-title":"Annu. Rev. Fish Dis."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"191","DOI":"10.1111\/j.1095-8649.1990.tb05851.x","article-title":"A quantitative and histochemical study on melano-macrophage centers in the spleen of the teleost fish Diplodus annularis L","volume":"37","author":"Micale","year":"1990","journal-title":"J. Fish Biol."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Agius, C. (1985). The Melano-Macrophage Centres of Fish: A Review. Fish Immunology, Academic Press Inc.","DOI":"10.1016\/B978-0-12-469230-5.50011-8"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1111\/j.1600-0749.2006.00319.x","article-title":"Isolation of the Atlantic salmon tyrosinase gene family reveals heterogenous transcripts in a leukocyte cell line","volume":"19","author":"Thorsen","year":"2006","journal-title":"Pigment. Cell Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1002\/aja.1001760303","article-title":"Mechanisms of splenic control of murine malaria: Reticular cell activation and the development of a blood-spleen barrier","volume":"176","author":"Weiss","year":"1986","journal-title":"Am. J. Anat."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"3823","DOI":"10.1016\/j.psj.2020.05.012","article-title":"Morphological characterization of postembryonic development of blood\u2013spleen barrier in duck","volume":"99","author":"Xu","year":"2020","journal-title":"Poult. Sci."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"343","DOI":"10.1111\/j.1462-5822.2011.01741.x","article-title":"The role of the spleen in malaria","volume":"14","author":"Ferrer","year":"2012","journal-title":"Cell. Microbiol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1002\/ar.1092410303","article-title":"Reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.): An ultrastructural and cytochemical study","volume":"241","author":"Meseguer","year":"1995","journal-title":"Anat. Rec."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"715","DOI":"10.3390\/biology4040715","article-title":"Neutrophil Development, Migration, and Function in Teleost Fish","volume":"4","author":"Havixbeck","year":"2015","journal-title":"Biology"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1007\/s00418-024-02313-w","article-title":"Distribution and morphologic characterization of telocytes in rat ovary and uterus: Insights from ultrastructural and immunohistochemical analysis","volume":"162","author":"Purelku","year":"2024","journal-title":"Histochem. Cell Biol."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Hussein, M.T., Zaccone, G., Albano, M., Alesci, A., Marino, S., Alonaizan, R., and Mokhtar, D.M. (2025). Serotonin Signaling and Macrophage Subsets in Goldfish Gills: Unraveling the Neuroimmune Network for Gill Homeostasis. Life, 15.","DOI":"10.3390\/life15050751"},{"key":"ref_48","first-page":"101","article-title":"Notes about telocytes and immunity","volume":"62","author":"Aleksandrovych","year":"2022","journal-title":"Folia Med. Cracov."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"09636897211002762","DOI":"10.1177\/09636897211002762","article-title":"Telocytes enhance M1 differentiation and phagocytosis while inhibits mitochondria-mediated apoptosis via activation of NF-\u03baB in macrophages","volume":"30","author":"Huang","year":"2021","journal-title":"Cell Transplant."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Mokhtar, D.M., Zaccone, G., Alesci, A., Kuciel, M., Hussein, M.T., and Sayed, R.K.A. (2023). Main Components of Fish Immunity: An Overview of the Fish Immune System. Fishes, 8.","DOI":"10.3390\/fishes8020093"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1269","DOI":"10.3389\/fimmu.2018.01269","article-title":"The Confluence of Sex Hormones and Aging on Immunity","volume":"9","author":"Potluri","year":"2018","journal-title":"Front. Immunol."}],"container-title":["Veterinary Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2306-7381\/12\/6\/517\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T17:39:56Z","timestamp":1760031596000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2306-7381\/12\/6\/517"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,5,25]]},"references-count":51,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2025,6]]}},"alternative-id":["vetsci12060517"],"URL":"https:\/\/doi.org\/10.3390\/vetsci12060517","relation":{},"ISSN":["2306-7381"],"issn-type":[{"value":"2306-7381","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,5,25]]}}}