Autoimmune sialadenitis: possible models for Sjögren's syndrome and a common aging phenomenon

Animal models of Sjögren's syndrome

Sjögren's syndrome is an autoimmune, chronic inflammatory disease characterized by focal mononuclear cell infiltration of exocrine tissues, accompanied by loss of secretory function. The pathogenesis of autoimmune diseases is complex and, therefore, difficult to study in vitro. As of today, the role of initiating factors remains obscure, clinical symptoms develop late, and there are no tests for early diagnosis of SS. Hence, the disease is difficult to detect and treat. Animal models may provide insights into the identification of target antigens, narrowing the relevant pathological immune mechanisms, and to study the evolution of tissue pathology. This review summarizes current knowledge on murine strains, both spontaneous and induced models, used to study Sjögren's syndrome. Special attention is paid to the characteristics of different strains regarding their properties to mimic specific aspects or stages of the disease.

Production of experimental autoimmune sialadenitis in mice immunized with homologous salivary gland extract and Klebsiella O3 lipopolysaccharide

An experimental murine model for autoimmune sialadenitis was produced by repeated immunization of homologous salivary gland extract together with Klebsiella O3 lipopolysaccharides as an immunological adjuvant. The cell infiltration was observed in the salivary glands of mice immunized more than twice. Inflammatory cells consisting mainly of CD4+ T cells and CD8+ T cells accumulated at the perivascular regions. There was hyperplasia and enlargement of ductal epithelial cells in the secretory acinar units in salivary glands of repeatedly immunized mice. The repeated immunization developed delayed-type hypersensitivity and autoantibody production to the homologous salivary gland extract. The immunohistochemical analysis showed positive staining on the cuboidal cells in the intercalated ducts, and the columnar pseudostratified cells in the striated ducts. Organ-specific antigens with molecular weights ranging from 20 to 90 kDa were recognized by the sera from immunized mice. Therefore, it was suggested that the sialadenitis was produced by the autoimmune mechanism and might be a new experimental model for characterization of the pathogenesis of autoimmune sialadenitis.

Sialadenitis in IQI/Jic mice: a new animal model of Sjögren's syndrome

Focal infiltration of lymphocytes with parenchymal destruction was noted in both salivary and lacrimal glands of IQI/Jic mice. The sialadenitis was found in more than 80% of female mice at all ages examined. The lesion progressed after 6 months and became more prominent with age. In contrast, male mice had slight and stable salivary lesions independent of age, though the incidence increased with age. Infiltrating lymphocytes consisted of both T and B cells. The dominant lymphocytes in small foci were CD4+ cells, but the majority of infiltrating cells were B cells (B220+), followed by CD4+ T cells in larger lesions. The ductual epithelium in the foci aberrantly expressed MHC class II antigen. Eight of 24 15-month-old female mice with sialadenitis produced speckled-type IgG antinuclear autoantibody. These findings are similar to those in patients with Sjögren's syndrome. IQI/Jic mice could be a novel animal model of Sjören's syndrome.

Impaired sweating as an exocrine manifestation in Sjögren's syndrome

To examine the prevalence of hypohidrosis and to quantitate sweating as an exocrinopathy in Sjögren's syndrome (SS), 49 patients with SS (primary form, 38; secondary form, 11) were studied. Sweating was induced by mental stimulation such as deep breathing or hand grasping. Statistically significant reductions of sweat volume were seen in SS (P < 0.005). Patients under 50 years old showed impaired sweat function compared with normal controls (P < 0.0005). In a control study, only haemodialysis patients showed impairment of sweating and this was greater than in patients with SS aged under 50 years. These results suggest that patients with SS develop impaired sweating as an exocrine manifestation in addition to the known symptoms of xerostomia and xerophthalmus.

Prevalence of eyelid dermatitis in primary Sjögren's syndrome

BACKGROUND

The eyelid dermatitis seen in elderly patients is a relatively heterogenous and troublesome disease. Most cases seem to be idiopathic and show resistance to standard dermatologic therapy.

METHODS

Fifty-two patients with primary definite Sjögren's syndrome (4 men, 48 women, mean age 54 years) were enrolled in this study, and the prevalence of eyelid dermatitis was investigated. Diagnostic criteria for Sjögren's syndrome were based on the criteria proposed by the Japanese Ministry of Health and Welfare. Patch test was performed using ICDRG-European standard allergens and/or eye drops, hair dye, and cosmetics.

RESULTS

Of the 52 patients, 22 showed eyelid dermatitis. These changes were much more frequent in elderly patients and showed a good correlation with the presence of ocular dry sensation. No significant difference was observed in clinical and other laboratory findings between patients with or without eyelid dermatitis. Although 8 of the 13 patients showed positive patch test reaction to various allergens, no close relationship existed between the use of a suspected substance and the onset or severity of eyelid dermatitis.

CONCLUSIONS

These results suggest that the presence of rubbing dermatitis of the eyelid may be one of the cutaneous manifestations of Sjögren's syndrome.