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Updated: Apr 11, 2026
Flow Cytometric Characterization of Murine B Cell Development
Published on: January 22, 2021
Functional characterization of IgM+ B cells and adaptive immunity in lumpfish (Cyclopterus lumpus L.)
Anita Rønneseth1, Dawit B Ghebretnsae1, Heidrun I Wergeland1
1Department of Biology, Bergen High-Technology Centre, University of Bergen, PO box 7803, NO-5020 Bergen, Norway.
Insights
Lumpfish B cells, identified by IgM, show significant phagocytic ability, playing a key role in innate immunity. This finding supports the potential for vaccination and immunostimulation in farmed lumpfish to prevent disease.
Area of Science:
- Immunology
- Fish Biology
- Aquaculture
Background:
- Innate immune responses in lumpfish (Cyclopterus lumpus L.) are functional, but adaptive immunity, particularly B cells and immunoglobulins, remains poorly understood.
- Limited knowledge exists regarding the specific roles and characteristics of B cells in lumpfish immune responses.
Purpose of the Study:
- To characterize B cells and their immune functions in lumpfish.
- To investigate the presence and capacity of adaptive immune responses in lumpfish.
- To explore the potential for disease prevention strategies in farmed lumpfish.
Main Methods:
- Isolation of B cells using anti-IgM antiserum from peripheral blood leukocytes (PBL), head kidney leukocytes (HKL), and spleen leukocytes (SL).
- Morphological and functional comparison of isolated B cells with other leukocyte types.
- Assessment of phagocytic activity and enzyme expression (acid phosphatases - AcP, myeloperoxidase - MPO) in different cell populations.
- Evaluation of specific antibody production following immunization to verify adaptive immunity.
Main Results:
- The fraction of IgM(+) B cells varied across tissues: 40% in PBL, 12% in HKL, and 34% in SL.
- IgM(+) B cells exhibited high phagocytic ability, particularly in PBL, exceeding that of IgM(+) B cells in HKL.
- Small, uncharacterized IgM(-) cells in PBL also demonstrated potent phagocytic capacity.
- IgM(+) B cells were positive for AcP and negative for MPO, while neutrophils were MPO-positive.
- Monocytes/macrophages and IgM(-) cells showed strong AcP positivity, correlating with high phagocytosis.
- Lumpfish demonstrated the ability to produce specific antibodies upon immunization, confirming adaptive immunity.
Conclusions:
- Phagocytic IgM(+) B cells play a significant role in lumpfish innate immunity.
- The presence of adaptive immunity suggests lumpfish can be effectively vaccinated.
- Findings indicate that vaccination and immunostimulation could be viable strategies to combat diseases in farmed lumpfish, reducing mortality.
Abstract:
The innate immune responses in lumpfish (Cyclopterus lumpus L.) have been shown to be functional, but little is currently known about the B cells, immunoglobulins or adaptive immune responses in this species. We have used anti-IgM antiserum to isolate B cells and compared them morphologically and functionally with other cell types. The fraction of IgM(+) cells among isolated peripheral blood leukocytes (PBL), head kidney leukocytes (HKL) and spleen leukocytes (SL) was in the range of 40%, 12% and 34%, respectively. The IgM(+) B cells had high phagocytic ability and were the predominant phagocytes in blood with higher capacity than IgM(+) B cells in HKL. Interestingly, among PBL, the most potent phagocytes were, in addition to monocytes, some small agranular uncharacterized IgM(-) cells. The IgM(+) B cells were positive for acid phosphatases (AcP), but negative for myeloperoxidase (MPO). Neutrophils were positive for MPO, while monocytes/macrophages and dendritic-like cells stained negatively. Monocytes/macrophages and the small, agranular IgM(-) cells stained most strongly positive for AcP corresponding to their high phagocytic capacity. Further, the ability to produce specific antibodies upon immunization verified adaptive immunity in the species. The high proportion of phagocytic IgM(+) B cells and their phagocytic ability indicate a significant role of phagocytic B cells in lumpfish innate immunity. The present analyses also give strong indications that vaccination and immunostimulation of farmed lumpfish can be used to prevent disease and mortality caused by pathogenic organisms.
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