Splenic outer periarterial lymphoid sheath (PALS): An immunoproliferative microenvironment constituted by antigen-laden marginal metallophils and ED2-positive macrophages in the rat |
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Authors: | Dr Kenjiro Matsuno Taichi Ezaki Masahiko Kotani |
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Institution: | (1) Department of Anatomy, Kumamoto University Medical School, Kumamoto, Japan;(2) 2nd Department of Anatomy, Kumamoto University Medical School, Honjo 2-2-1, 860 Kumamoto, Japan |
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Abstract: | Summary In an attempt to reveal the role of antigen-laden marginal metallophil (MM) and other macrophages in the intrasplenic immune response of a specific B-cell lineage to a thymus-independent type-2 antigen (Ficoll conjugated with fluorescein isothiocyanate), simultaneous immuno-histological observations of the involved cells were performed in the rat. By newly established methods of double or triple immunostainings, time-kinetics of the following parameters were studied and compared: (1) the antigen, (2) the specific antibody-forming cells (AFC) directed to the fluorescein-isothiocyanate determinant, (3) proliferating cells labeled with 5-bromo-2-deoxyuridine (BrdU), and (4) macrophage subpopulations recognized by monoclonal antibodies (ED2 and ED3). The antigen localized stably not only in the marginal-zone macrophages but also in the MM except around the follicular area. The increase of BrdU-positive cells was observed from day 2 up to day 4 after antigen injection mostly in the periphery of the periarterial lymphoid sheath (outer PALS), which indicated antigen-induced proliferation. As a novel finding, the majority of AFC, both BrdU-positive and -negative, were either closely associated with the antigen-laden MM, or forming cell clusters with ED2-positive macrophages in the outer PALS. In contrast, there were very few AFC in juxtaposition to antigen-free MM in the follicular area or the antigen-laden marginal zone macrophages. The results led to the proposal of a hypothesis that the antigen-laden MM together with ED2-positive macrophages constitute an immunoproliferative microenvironment for the plasmacellular reaction by accumulating the antigen-specific B-cell lineage and promoting these cells to differentiate into the AFC and to proliferate in the outer PALS.Abbreviations
AFC
specific antibody-forming cells
- BrdU
5-bromo-2-deoxyuridine
- Fic-F
FITC-conjugated Ficoll
- FITC
fluorescein isothiocyanate
- HRP
horseradish peroxidase
- MM
marginal metallophils
- MZ
marginal zone
- PALS
periarterial lymphoid sheath
- PBS
phosphate-buffered saline
- TI2
thymus-independent type-2 |
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Keywords: | Spleen Periarterial lymphoid sheath (PALS) Macrophage subpopulations Microenvironment B-lymphocytes Immune response Cell proliferation Immunohistochemistry Rat (DA) |
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