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The lesser spotted dogfish, <i>Scyliorhinus canicula</i> was found to be capable of mounting a vigorous specific humoral response to the soluble immunogen bovine serum albumin in Freund's complete or incomplete adjuvants. The kinetics of the humoral response to all doses of bovine serum albumin were determined. Antibody levels peaked at ca. 15 weeks and were then maintained at a plateau level until the experiment was terminated (at 38/39 weeks). An investigation of the reticulo-endothelial system of the dogfish was conducted by monitoring the clearance of intravascularly injected materials from the circulation. Macrophages of the ellipsoids and red pulp of the spleen, fixed cells in an expanded area of the branchial arterial system of the gills, known as the cavernous body, and cells in the liver, some probably homologous to mammalian Kupffer cells, were principally responsible for the sequestration of the injected materials. Peripheral blood monocytes and thrombocytes were also found to partake in the clearance of materials. Significant changes in the relative counts of blood leucocytes concomitant with injection of these materials was noted. The chemotactic/chemokinetic potential of dogfish granulocytes was investigated using the migration under agarose and bipolar shape formation assays. In the former assay eosinophilic G1 and G3 granulocytes were tested against a range of known chemotactic agents (including synthetic formyl peptides, bacterial culture filtrates, eosinophil chemotactic factor of anaphylaxis and complement fragments), but none of these factors appeared capable of inducing either chemotaxis or chemokinesis. In the bipolar shape formation assay, neither granulocyte type responded to complement fragments or formyl peptides. However, leukotriene B<SUB>4</SUB>, a potent chemotactic factor for mammalian leucocytes, was found to induce chemotaxis/chemokinesis of G1 granulocytes in the migration under agarose assay, and bipolar shape formation of both G1 and G3 granulocytes in the bipolar shape formation assay.

The initial aim of this project was to raise monoclonal antibodies to the haemocytes of the marine mussel, <I>Mytilus edulis, </I>which were capable of distinguishing subpopulations of haemocytes. Thirteen monoclonal antibodies were raised, including 3 antibodies for all haemocyte types, 2 specific for eosinophilic haemocytes and 8 specific for different subpopulations of basophilic haemocytes. All the antibodies were found to bind to the granules and/or cytoplasm of the respective haemocyte types. These monoclonal antibodies have illustrated some common links between phylogenetically related molluscs. A total of 11 other species were tested from 3 taxonomic orders. Cross-reactivity was most likely in those species closest taxonomically to <I>M. edulis, </I>and was also most probable with the non-selective antibodies. Functional studies have examined the effects of the monoclonal antibodies, and six others kindly provided by Dr. D. Noël (DRIM, University of Montpellier), on cell adhesion and phagocytosis. No significant differences were observed in phagocytosis, however, some indication exists of the involvement of monoclonal antibody 19E10 in cellular adhesion. The reactivity of the monoclonal antibodies with larval cells and adult tissue sections appears to be a promising technique for targeting potential haemopoietic sites. Reactivity with the antibodies was observed in undifferentiated larval cells and in adult connective tissue, the latter has previously been suggested as a haemopoietic site in bivalves. As part of the research into immune ontogeny, the immune response of the larvae of <I>M. edulis </I>has also begun to be characterized, using a disaggregation technique. To date, the enzymes arylsulphatase and phenoloxidase have been identified, and phagocytosis has been quantified in larval cells. The generation of superoxide anion has also been detected, although the levels observed were found to vary considerably with the techniques employed to manipulate the cells.

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