{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,29]],"date-time":"2026-07-29T23:57:38Z","timestamp":1785369458387,"version":"3.55.0"},"reference-count":59,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2022,9,26]],"date-time":"2022-09-26T00:00:00Z","timestamp":1664150400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["32102827"],"award-info":[{"award-number":["32102827"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003453","name":"Natural Science Foundation of Guangdong Province","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100003453","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002858","name":"China Postdoctoral Science Foundation","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100002858","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100021171","name":"Basic and Applied Basic Research Foundation of Guangdong Province","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100021171","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Plasma cells are terminally differentiated antibody-secreting B lymphocytes that contribute to humoral immunity by producing large numbers of antibodies. Increasing evidence suggests that teleost fish B cells share certain characteristics with mammalian B1 B cells, including antibody-secreting, phagocytic, and antigen-presenting capacities. However, the difference between mature B cells and plasma cells remains unclear. In this study, we found that, based on their light-scattering characteristics, tilapia anterior kidney (AK) leukocytes can be categorized into two IgM<jats:sup>+<\/jats:sup> B-cell subsets: the lymphoid (L) gate and granulocyte\u2013monocyte\/macrophage (G-M) subsets. G-M gate cells are more numerous than L-gate cells and have higher mean fluorescence, but lower forward scatter and side scatter. We analyzed the morphological and ultrastructural features of sorted IgM<jats:sup>+<\/jats:sup> cells and found that L-gate IgM<jats:sup>+<\/jats:sup> cells have a high nucleus\u2013cytoplasm ratio and lymphocyte-like morphology, whereas G-M gate IgM<jats:sup>+<\/jats:sup> cells have a small nucleus, more abundant endoplasmic reticulum, and a larger number of mitochondria, and have a plasma cell-like or macrophage-like morphology. To further characterize the cell types, we examined the specific patterns of expression of B-cell- and T-cell-related genes. We found that B-cell-specific genes were expressed by both L-gate and G-M gate IgM<jats:sup>+<\/jats:sup> cells, and that G-M gate IgM<jats:sup>+<\/jats:sup> cells secreted extremely high levels of IgM. However, T-cell-related genes were highly expressed only in L-gate IgM<jats:sup>\u2013<\/jats:sup> cells. These results suggest that G-M gate IgM<jats:sup>+<\/jats:sup> cells are similar to plasma-like cells, with high antibody-secreting capacity. Given that G-M gate cells include the granulocyte, monocyte, and macrophage cell types, but not B cells, monocyte\/macrophage markers were used to investigate the cell types further. A macrophage receptor with a collagenous structure was frequently observed, and macrophage-expressed gene-1 was highly expressed, in the G-M gate IgM<jats:sup>+<\/jats:sup> cells. Phagocytic capacity, as determined by ingestion of beads or bacteria, was significantly higher in G-M gate IgM<jats:sup>+<\/jats:sup> cells than in L-gate IgM<jats:sup>+<\/jats:sup> cells, as was antigen-processing capacity. Our findings show that tilapia AK leukocytes can be divided into two IgM<jats:sup>+<\/jats:sup> B-cell subsets and that G-M gate IgM<jats:sup>+<\/jats:sup> cells resemble plasma-like cells, having high antibody-secreting, phagocytic, and antigen-presenting capacities. Thus, this study increases our understanding of the functions of teleost fish plasma-like cells.<\/jats:p>","DOI":"10.3389\/fimmu.2022.1016974","type":"journal-article","created":{"date-parts":[[2022,9,27]],"date-time":"2022-09-27T09:09:51Z","timestamp":1664269791000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":17,"title":["Teleost fish IgM+ plasma-like cells possess IgM-secreting, phagocytic, and antigen-presenting 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