Expression of caveolin‐1 in the interfollicular but not the follicle‐associated epithelial cells in the bursa of fabricius of chickens |
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| Authors: | Orsolya Fölker Zsófia Benyeda Balázs Felföldi Attila Magyar Anna Kiss Vilmos Palya Imre Oláh |
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| Affiliation: | 1. Department of Anatomy Histology and Embryology, Semmelweis University, Budapest, Hungary;2. Biovo Animal Health Ltd, Mohács, Hungary;3. A Ceva Animal Health (Ceva‐Phylaxia), Szállás utca 5, 1107 Budapest, Hungary |
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| Abstract: | The surface epithelium of the bursa of Fabricius consists of interfollicular (IFE) and follicle‐associated epithelium (FAE). The IFE comprises (i) cylindrical‐shaped secretory cells (SC) and (ii) cuboidal basal cells (BCs). The FAE provides histological and two‐way functional connections between the bursal lumen and medulla of the follicle. We used a carbon solution and anti‐caveolin‐1 (Cav‐1) to study the endocytic activity of FAE. Carbon particles entered the intercellular space of FAE, but the carbon particles were not internalized by the FAE cells. Cav‐1 was not detectable in the FAE cells or the medulla of the bursal follicle. The absence of Cav‐1 indicates that no caveolin‐mediated endocytosis occurs in the FAE cells, B cells, bursal secretory dendritic cells (BSDC), or reticular epithelial cells. Surprisingly, a significant number of Cav‐1 positive cells can be found among the SC, which are designated SC II. Cav‐1 negative cell are called SC I, and they produce mucin for lubricating the bursal lumen and duct. Occasionally, BCs also express Cav‐1, which suggests that BC is a precursor of a SC. Transmission electron microscopy confirmed the existence of type I and II SC. The SC II are highly polarized and have an extensive trans‐Golgi network that is rich in different granules and vesicles. Western blot analysis of bursa lysates revealed a 21–23 kDa compound (caveolin) and Filipin fluorescence histochemistry provided evidence for intracellular cholesterol. High amount of cholesterol in the feces shows the cholesterol efflux from SC II. The presence of Cav‐1 and cholesterol in SC II indicates, that the bursa is a complex organ in addition to possessing immunological function contributes to the cholesterol homeostasis in the chickens. |
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| Keywords: | basal cell differentiation cholesterol homeostasis secretory cell type I secretory cell type II |
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