The long term goal of this proposal is to characterize the mechanism of tissue damage in connective tissue disease (CTD) using the lymphocytic infiltration of exocrine glands in Sjogren's Syndrome (SS) as a model. This model of inflammation and destruction provides a unique and important opportunity to investigate the complex orchestration of lymphocytes and their relationship to cell damage which may also affect major organs notably lungs, liver and kidney. Understanding these phenomena is essential to the development of therapeutic modalities for CTDs. CTDs including primary and secondary SS are of increasing importance in an aging population where they cause significant morbidity and mortality.(12) This project addresses a priority area of """"""""Healthy People 2000"""""""" in that autoimmune sialoadenitis has been proposed as a model of aging.(1) Sjogren's Syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration and destruction of exocrine glands, hypergammaglobulinemia and autoantibodies.(3,6) Since the majority of lymphocytes are CD4+ activated helper T-cells(2,3,4,5,6) It has been presumed that destruction is mediated by those. This is an enigma since one would expect more CD8+ cytotoxic cells and antigen presenting cells to be present. Furthermore, plasma cells occur at an early stage and salivary glands produce immunoglobulin, rheumatoid factor and IL-2, but the relationship of these or autoantibodies to destruction is unclear.(2,3,6) Attempts to implicate viruses in SS have been inconclusive. Preliminary studies in our laboratory have shown that there is an abnormal intracellular accumulation of laminin in ductal epithelia(8) of SS patients. Our hypothesis is that laminin is trapped within the cell as a result of mistargeting to the basal surface. This intracellular signaling defect causes the structural changes in the basement membrane and loss of cell polarity seen by light microscopy. We propose that loss of basement membrane integrity leads to epithelial atrophy and release of inflammatory compounds which mediate lymphocytic infiltration. To test this hypothesis the following experiments are planned: 1) the specific localization of laminin in ductal epithelial cells and the extracellular matrix will be compared by immunogold and electron microscopy; 2) laminin mRNA expression in SS and normal ductal epithelial will be evaluated by in situ hybridization using a cDNA probe; 3) laminin expression by ductal epithelia in SS will be compared in ducts with and without lymphocytic infiltration; and 4) beta-integrin (laminin receptor) and CD44 (lymphocyte homing receptor) expression will be compared in ducts with and without lymphocytes. If Experiment 1 shows laminin is predominantly intracellular and therefore abnormal in location, this would provide compelling evidence for an intracellular signaling defect. The finding of increased laminin mRNA would be consistent with increased laminin expression shown by light microscopy.(8) Experiment 3 examines the temporal relationship between laminin and the presence of lymphocytes. Preliminary evidence regarding the mechanism of lymphocyte homing to these glands will be obtained from Experiment 4.
| Daniels, P J; McArthur, C P; Heruth, D P et al. (1999) Cytokine-mediated stimulation of laminin expression and cell-growth arrest in a human submandibular gland duct-cell line (HSG). Arch Oral Biol 44:603-15 |
| McArthur, C P; Daniels, P J; Kragel, P et al. (1997) Sjogren's syndrome salivary gland immunopathology: increased laminin expression precedes lymphocytic infiltration. J Autoimmun 10:59-65 |
