We recently observed, over the tunic covering the inner side of both the siphons of the compound ascidian Botryllus schlosseri (Urochordata), the presence of granular amoebocytes, completely exposed to seawater. In order to understand the origin and biological role of these unusual amoebocytes we have investigated them by electron microscope and cytochemistry. They are mononucleate and with numerous round granules, various in content and have long filopodia, which contact the cuticle protrusions of the tunic in the siphon. Cytochemical, cytoenzymatic and immunocytochemical assays were carried out at light microscope on sections and in parallel experiments on fixed cultured haemocytes. Results showed that the phagocytic blood cells, i.e. hyaline amoebocytes, macrophage-like cells and signet-ring cells, and the free amoebocytes of the siphons, showed affinity to the -mannose specific agglutinin of Narcissus pseudonarcissus (NPA), and exhibited the hydrolytic activities of acid phosphatase and non-specific esterases inside lysosomal vesicles and large vacuoles. No phenoloxidase activity, typical of the cytotoxic blood cell line (morula cells) of this species, was detected. Moreover, anti-CD39 immunocytochemical assay for mammalian macrophages labelled the lysosomes of both phagocytes and free amoebocytes, whereas the positivity to anti-CD57 antibody for mammalian NK occurred in the morula cells but not in the amoebocytes. We consider these cells represent “sentinel-cells” belonging to the phagocytic line of the immune system since they share with the blood phagocytes the hydrolytic enzyme pattern, and the labelling by both NPA and anti-CD39 antibody, and can recognise and phagocytise target particles experimentally administered.

Cytochemical characterisation of free amoebocytes in the siphons of an ascidian

CIMA, FRANCESCA;GASPARINI, FABIO;
2003

Abstract

We recently observed, over the tunic covering the inner side of both the siphons of the compound ascidian Botryllus schlosseri (Urochordata), the presence of granular amoebocytes, completely exposed to seawater. In order to understand the origin and biological role of these unusual amoebocytes we have investigated them by electron microscope and cytochemistry. They are mononucleate and with numerous round granules, various in content and have long filopodia, which contact the cuticle protrusions of the tunic in the siphon. Cytochemical, cytoenzymatic and immunocytochemical assays were carried out at light microscope on sections and in parallel experiments on fixed cultured haemocytes. Results showed that the phagocytic blood cells, i.e. hyaline amoebocytes, macrophage-like cells and signet-ring cells, and the free amoebocytes of the siphons, showed affinity to the -mannose specific agglutinin of Narcissus pseudonarcissus (NPA), and exhibited the hydrolytic activities of acid phosphatase and non-specific esterases inside lysosomal vesicles and large vacuoles. No phenoloxidase activity, typical of the cytotoxic blood cell line (morula cells) of this species, was detected. Moreover, anti-CD39 immunocytochemical assay for mammalian macrophages labelled the lysosomes of both phagocytes and free amoebocytes, whereas the positivity to anti-CD57 antibody for mammalian NK occurred in the morula cells but not in the amoebocytes. We consider these cells represent “sentinel-cells” belonging to the phagocytic line of the immune system since they share with the blood phagocytes the hydrolytic enzyme pattern, and the labelling by both NPA and anti-CD39 antibody, and can recognise and phagocytise target particles experimentally administered.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2453748
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