No abstract

Estrogenic action has been suggested to be responsible for the strong female preponderance of autoimmune diseases, but the role of estrogens in the female has not been well characterized. We evaluated the effects of estrogen deficiency in a murine model for autoimmune exocrinopathy of Sjögren's syndrome (SS). Severe destructive autoimmune lesions developed in the salivary and lacrimal glands in estrogen-deficient mice, and these lesions were recovered by estrogen administration. We detected an intense estrogen receptor in splenic CD8(+) T cells compared with that in CD4(+) T cells, and concanavalin-A-stimulated blastogenesis of splenic CD8(+) T cells with estrogens was much higher than that of CD4(+) T cells. We found a significant increase in serum autoantibody production against the organ-specific autoantigen alpha-fodrin. Moreover, an increased proportion of TUNEL+ apoptotic epithelial duct cells was observed in estrogen-deficient mice. It was demonstrated that Fas-mediated apoptosis in cultured salivary gland cells was clearly inhibited by estrogens in vitro. These results indicate that dysfunction of regulatory T cells by estrogen deficiency may play a crucial role on acceleration of organ-specific autoimmune lesions, and estrogenic action further influences target epithelial cells through Fas-mediated apoptosis in a murine model for SS.

It is unclear whether organ-specific autoantigens are critical for the development of primary Sjögren's syndrome (SS). A 120-kilodalton organ-specific autoantigen was purified from salivary gland tissues of an NFS/sld mouse model of human SS. The amino-terminal residues were identical to those of the human cytoskeletal protein alpha-fodrin. The purified antigen induced proliferative T cell responses and production of interleukin-2 and interferon-gamma in vitro. Neonatal immunization with the 120-kilodalton antigen prevented the disease in mice. Sera from patients with SS reacted positively with purified antigen and recombinant human alpha-fodrin protein, whereas those from patients with systemic lupus erythematosus and rheumatoid arthritis did not. Thus, the immune response to 120-kilodalton alpha-fodrin could be important in the initial development of primary SS.

SUMMARYThe NOD mouse develops spontaneous autoimmune lesions in the lacrimal and salivary glands, besides a well characterized T cell-mediated autoimmune pancreatic b cell lesion. We report unique pathological findings developed in the lacrimal glands as an autoimmune dacryoadenitis of NOD mice in contrast to those found in the salivary glands and pancreas. A high incidence of autoimmune lesions in the lacrimal glands was observed exclusively in male NOD mice at any age. Histology of autoimmune dacryoadenitis in male NOD mice showed severe destructive changes compared with those observed previously as an autoimmune lesion in the lacrimal glands. Castration in male NOD mice significantly decreased the incidence of autoimmune dacryoadenitis, and testosterone treatment with castration also increased the incidence of autoimmune lesions. Oestrogen treatment with castration did not increase the incidence, but tamoxifen treatment without castration significantly increased the incidence of autoimmune dacryoadenitis in NOD mice. In addition, we detected up-regulation of local cytokine genes (IL-1b, tumour necrosis factor-alpha (TNF-a), IL-2, interferon-gamma (IFN-g), IL-6, IL-10, and IL-12 p40) during the course of autoimmune dacryoadenitis. These data suggest that in spontaneous autoimmune dacryoadenitis of male NOD mice there may be an intimate relationship with sex steroids, particularly testosterone, in the development and progression of autoimmune lesions, and autoreactive Th1 cells secrete up-regulated cytokine genes, including IL-10 and IL-12.