A study of salivary glands and saliva in health and disease.
Much of this thesis describes the use of immunohistochemical methods on salivary glands
from patients with Sjogren's syndrome (SS) to quantify the position, nature and
proliferative activity of the inflammatory cell infiltrate, deposition of cell matrix proteins
and glandular expression of TGFp. Studies are also undertaken on glands from an
experimental animal model and from patients with two associated conditions, benign
lymphoepithelial lesion (BLEL) and systemic sclerosis (SSc).
Initially a rat model of SS was examined and changes in salivary glands quantified at
different stages after autoimmunisation. Immunohistochemically there were similarities to
SS, in that class II antigen was expressed by glandular epithelium and the early lesions
contained T lymphocytes. However, B lymphocytes were rare, the cell infiltrate contained
large populations of macrophages and neutrophils, and there was evidence of increased
elaboration of fibrous connective tissue. These results indicate that this animal model is of
doubtful use for the study of Sjogren's syndrome.
Studies on human tissue showed that the lymphocyte infiltrate in BLEL patients was more
extensive than SS and that T cells predominated in small foci, whereas B cells were the
dominant lymphocyte type in larger foci. In areas of extensive lymphocyte infiltration, B
cells were closely associated with ducts or present in germinal centre-like structures with T
cells being found elsewhere. A previously unreported feature of BLEL was the presence
of intra-epithelial (and intra-lumenal) B cells, many of which were proliferating. The
remaining duct walls in BLEL appeared to be under pressure due to this population of B
lymphocytes and "holes" were observed both in the basement membrane and at the
lumenal surface that may facilitate migration of lymphocytes from glandular stroma into
There was significantly more tenascin and fibronectin in BLEL glands (p<0.01) compared
to normal parotid controls which contained minimal amounts of these proteins. By
contrast, both proteins were expressed in normal labial glands with no significant increase
in glands from SS and SSc patients. As both tenascin and fibronectin are important in cell migration, increased levels may be a factor facilitating lymphoid infiltration in BLEL.
Absorbance measurements demonstrated that ductal expression of TGFI differed between
control, SS and BLEL salivary glands. SS glands showed an increase in expression of all
isoforms of TGFß with the increase for TGFP2 and TGFP3 being significant (p=0.02 &
p<0.002). By contrast, ductal expression of all isoforms of TGFI in BLEL was reduced in
both confluent (p<0.0001) and minimally infiltrated (p<0.005) areas of gland. Thus
reduced glandular expression of TGFJ may be important in allowing the high levels of
lymphocyte and epithelial cell proliferation detected in BLEL which are rarely seen in SS.
Salivary glands from SSc and Raynaud's phenomenon (RP) patients contained small,
predominately T cell foci with few proliferating B cells and a significantly increased mast
cell population (p<0.005). Fibrosis within the glands was variable and not associated
with increased deposition of fibronectin or tenascin. Subjectively, the most obvious
difference in TGFI expression in SSc compared to controls was exhibited by fibroblasts.
Cell counts revealed no differences in fibroblast expression of TGFßI or TGFß receptors.
However, the percentage of TGFß2-positive fibroblasts was significantly higher in SSc
glands compared to controls (p<0.004). RP glands showed an intermediate level of
expression. By contrast, a lower percentage of RP fibroblasts expressed TGF(33 compared
to controls, with SSc glands showing an intermediate level of expression. The results
indicate that both SSc and RP are associated with an increased salivary gland mast cell
population and changes in expression of TGFß2 and ß3 isoforms by glandular fibroblasts.
The final section of this thesis describes an investigation of antioxidant levels in saliva
from healthy individuals and patients with SS or periodontal disease. The results
demonstrated that in SS there was an increase in the concentration of antioxidants in
unstimulated saliva but a reduced rate of production. This diminished output of salivary
gland antioxidants may be of significance to the oral health of these patients. In
periodontal disease there was a reduction in antioxidant levels in stimulated saliva that
may have been the result of local depletion by reactive oxygen species, produced by
chronic inflammation within the gingival tissues. Alternatively, these patients may have
intrinsically reduced levels of antioxidants and therefore be more susceptible to