Immunophenotyping of Mya arenaria neoplastic hemocytes using propidium iodide and a specific monoclonal antibody by flow cytometry.

Disseminated neoplasia (DN) is a disorder referred to as hemic neoplasia (HN) in the soft-shell clam Mya arenaria. Traditionally, diagnosis is performed by hematocytology or histology. The intensity of the disease is generally given as the percentage of transformed neoplastic cells out of total number of hemocytes. Flow cytometry techniques have found a field of application in diagnosis of HN with analysis of ploidy. Hemocytes of the soft-shell clams with HN display tetraploid DNA content, as shown by propidium iodide staining. This feature makes difficult HN diagnosis in the soft-shell clam, especially for early stages of the condition, since the percentage of normal circulating cells undergoing mitosis, which also are tetraploid, remains unknown in molluscs. Use of specific monoclonal antibodies in a flow cytometry assay was foreseen as a way to overcome the difficulty. The purpose of this study was to develop a double staining protocol using propidium iodide for hemocyte cycle analysis and the MAb 1E10 for staining of HN cells. Our results showed a correlation between tetraploid and MAb 1E10-stained hemocytes in a single clam with moderate HN. This protocol offers some potential for further investigation of this cell disorder. However, a validation step will be necessary to confirm our preliminary results.