A Origem das Células de Defesa (hemócitos) em Biomphalaria glabrata (Say, 1818). / The origin of the cells of defense (hemocytes) in Biomphalaria glabrata.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The defensive reactions against micro-organisms in snails of the genus Biomphalaria are performed by a single cell type the hemocyte or amebocyte. These cells, phagocytic and mobile, exist in the interior of the tissues and circulate in the hemolymph. Its site of origin is still uncertain. It is admitted that these cells in Biomphalaria glabrata originate in an organ situated in the anterior wa ll of the pericardial sack denominated APO (?Amebocyte Producing Organ?). The occurrence of hyperplasia and mitoses within the APO during infection with Schistosoma mansoni has been taken as the main argument to consider this organ as a hematopoietic organ. This work looks at the location, form, and behavior of the APO in normal and S. mansoni-infected B. glabrata, aiming at understanding its role in defense reactions. The investigation was performed by means of a histopathological, morphometrical, ultra-structural an immuno-histochemical study. The APO appeared represented by collections of basophilic cells with round nucleus rich in chromatin, and a homogenous cytoplasm, forming rows alongside a narrow region of the pericardial membrane. There were mild variations in the APO of infected snails in comparison with non-infected controls. Presence of mitoses was not a differential feature. Electron microscopy revealed that the organ is formed by juxtaposed epithelial cells, rich in organelles, united by inter-digitations. Monoclonal antibody against the Ki67 antigen, which reveals a factor of nuclear proliferation, gave a strong positivity for sporocysts and cercarias, but failed to be expressed on snail tissues, including the APO. In the preparations where the AgNOR technique was applied, the positive results, indicative of nucleolar proliferative activity, appeared with a golden brown color in the interior of the nucleolus of cells in the process of division. The marking was expressed in APO and in cells from various organs, especially in those with clear cellular proliferation, such as the ovotestis and digestive glands, both in normal snails and in those infected. On the other hand, accumulation of hemocytes in the interior of various tissues and cavities of various organs, especially the heart, were observed in the animals infected. These findings correlate better with hypertrophy and hyperplasia of the lining cells from the lacunar spaces, than with the scarce modifications present in the APO. Conclusion: Hemocytes in B. glabrata seem to originate from the endothelial lining of the vascular spaces throughout the snail body, as suggested in earlier studies rather than from a unique central organ, the APO.

ASSUNTO(S)

ki67 hemócitos hemócitos biomphalaria glabrata ki67 biomphalaria glabrata schistosoma mansoni apo apo schistosoma mansoni imunologia

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