Studies were conducted to investigate the in vivo and in vitro 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 trypsinlike 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 ex vivo populations of isolated
intestinal mast cells and bone marrow derived mast cells grown in vitro.
In vivo studies comparing yearling goats and kids with lambs undergoing primary and
secondary infections with Telodorsagia circumcincta demonstrated that after 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,
kids and lambs developed increased mean total serum IgE levels after primary and secondary
exposure to nematodes.
Caprine mast cells were also studied in isolation through ex vivo purification of
caprine intestinal mucosal mast cells (MMC) and GL and in vitro growth of bone marrow
marrow derived mast cells (BMMC) from haemopoietic precursor cells using recombinant
ovine cytokines. Caprine and ovine BMMC cultures were characterised in terms of their cell
morphology, GMCP, SMCP and acid hydrolase content during cytokine dose and time
response experiments, which demonstrated the significant effects of ovine stem cell factor on
BMMC proliferation and long term culture viability when used in combination with ovine
interleukin-3. Biochemical and morphological studies, including the use of electron
microscopy, were carried out to compare isolated goat MMC with goat and sheep BMMC as
well as with isolated sheep MMC. These highlighted significant differences in the mediator
content of the different cell populations with markedly less protease in caprine BMMC when
compared with ovine BMMC and caprine MMC.
Goat MMC and BMMC were stimulated to release the contents of their cytoplasmic
granules in the presence of synthetic secretogogues and crude nematode antigen preparations.
Initial results showed that calcium ionophore A21387 produced the greatest dose-related
release of mediators from caprine BMMC, indicating that the majority of the cells present in
these cultures possessed a functional phenotype similar to that associated with MMC.
Subsequent studies involving crude antigen preparations derived from T. circumcincta and
Haemonchus contortus demonstrated that they were capable of inducing BMMC activation.
This activation response could also be enhanced after passive sensitisation of the cells with
IgE-containing serum or lymph preparations obtained from animals undergoing experimental
exposure to parasitic nematodes.