Objective: To explore the possibility to establish Sjögren's syndrome models by immunizing mice with alpha-fodrin.
Methods: Twenty-four 4-week-old BALB/C mice were randomly divided into 4 equal groups to undergo subcutaneous injection of alpha-Fodrin, submaxillary gland homogenate and glutathione S-transferase (GST) or phosphate-buffered saline (PBS) (negative control groups) on days 0, 14, 35, and 56 respectively. The drinking amount of water was measured. Blood samples were collected every 2 - 3 weeks. Munofluorescence assays and ELISA were used to examine the presence of anti-Fodrin, anti-type 3 muscarinic acetylcholine receptor polypeptide (M3RP), anti-SSA, anti-SSB, rheumatoid factor (RF), and antinuclear antibody (ANA). Immunochemistry was used to detect the levels of interferon (IFN)-gamma, interleukin (IL)-2, and IL-10. One mouse was killed from each group every 2 - 3 weeks. The salivary glands were examined.
Results: (1) No auto-immune antibody was found in the serum samples of the mice before immunization. Antibodies against alpha-Fodrin and M2RP, and ANA were positive in the serum samples of the alpha-Fodrin and submaxillary gland homogenate groups since the 35th day after immunization, and were all negative in the 2 control groups. However, no antibodies against SSA, SSB and RF were found in all 4 groups. (2) Lymphocytic infiltration could be seen in the salivary glands of the immunized animals since 50th days after the first immunization of alpha-Fodrin and submaxillary gland homogenate. Immunohistochemistry showed alpha-Fodrin expression in the submaxillary glands of the alpha-Fodrin and submaxillary gland homogenate groups, but not in the PBS and GST controls. (3) The serum IFN-alpha levels of the alpha-Fodrin and submaxillary gland homogenate groups were (81.6 +/- 7.1) and (90.5 +/- 4.9) pg/ml respectively, both significantly higher than those of the GST and PBS groups [(30.1 +/- 5.9) and (19.3 +/- 6.4) pg/ml respectively, both P < 0.05]. The serum IL-2 levels of the alpha-Fodrin and submaxillary gland homogenate groups were (18.7 +/- 2.3) and (19.8 +/- 0.9) pg/ml respectively, both significantly higher than those of the GST and PBS groups [(4.9 +/- 1.1) and (3.5 +/- 1.6) pg/ml respectively, both P < 0.05]. No difference was found in the level of serum IL-10 among the 4 groups. (4) There was no significant difference in the volume of water volume drunk among the 4 groups.
Conclusion: (1) It is possible to establish mouse mice SS models by immunization with alpha-Fodrin or submaxillary gland homogenate that are reminiscent of human SS. (2) The appearance of multiple antibodies may be related to the antigen epitope spreading. (3) The pathogenesis of SS may be related to Th1 type response.