| Summary: | Studies were conducted to investigate the <I>in vivo</I> and <I>in vitro</I> responses of caprine mast cells to challenge with gastro-intestinal nematode parasites. Initial work concentrated on the isolation and purification of a mast cell-specific neutral granule protease, termed goat mast cell protease (GMCP), from homogenates of caprine intestinal tissue. Immunological, biochemical and molecular characterisation studies localised the enzyme to caprine mast cells, confirmed its similarity to a sheep mast cell protease (SMCP), uncovered cDNA coding for a second mast cell protease (termed GMCP II) and highlighted a dual chymotrypsin and trypsin-like substrate specificity. This latter finding categorised it alongside SMCP and bovine duodenase as a member of the novel 'janus' class of dual-specific ruminant serine esterases. Polyclonal and monoclonal antibodies were raised against GMCP and an enzyme linked immunosorbent assay (ELISA) constructed which was used to determine the functional activity of mast cells. This was achieved initially in the tissues of animals undergoing experimental infections with nematodes and subsequently in <I>ex vivo</I> populations of isolated intestinal mast cells and bone marrow derived mast cells grown <I>in vitro</I>. <I>In vivo</I> studies comparing yearling goats and kids and lambs undergoing primary and secondary infections with <I>Telodorsagia circumcincta</I> demonstrated that following secondary infections the goat and kid abomasal tissues retained more worms and, after both primary and secondary infections, contained considerably less GMCP than the equivalent lamb abomasal tissues. A significant mastocytosis response following repeated exposure to the parasites was also demonstrated in both species, although the secondarily infected goats and kids contained proportionately more globule leukocytes (GL) than the lambs. Blood and tissue eosinophil responses were variable, but measurements for total serum IgE demonstrated that the goats, kid and lambs developed increased mean total serum IgE levels following primary and secondary exposure to nematodes.
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