Murine models of Sjögren's syndrome. Evolution of the lacrimal gland inflammatory lesions.

Lacrimal gland inflammation develops in a number of autoimmune mice, including the MRL/Mp-lpr/lpr (MRL/lpr), MRL/Mp(-)+/+ (MRL/+), and NZB x NZW F1 hybrid (NZB/W) strains. The authors studied the evolution of this process, MRL/lpr mice had inflammatory lesions at 4 weeks old. The lesions had enlarged by 2 months and were fully developed by 4 to 5 months of age. In MRL/+ mice, 4-week-old mice had no lesions, although some focal inflammation was detectable at 3 months old. Significant abnormalities were present at 6 months, and persisted and increased throughout life, with all mice having extensive lesions at 18 months or older. In NZB/W mice, the authors detected no lesions until 6 months of age, and these lesions were fully developed in 9 months. Immunocytochemical profiles, of the cell types infiltrating the lacrimal gland, showed differences not only between the strains, but also in each strain as inflammation progressed. All three types of mice had L3T4+ T cells as the major lymphocyte component, although MRL/+ had significantly more Lyt 2+ T cells than the other strains. NZB/W mice had significantly more B cells than the two MRL substrains. In both NZB/W and MRL/+ mice, there was a significant increase in the B cell population, and a decrease in the percentage of L3T4+ T cells. There was a significant decline in Lyt 2+ T suppressor/cytotoxic cells in both NZB/W and MRL/lpr mice. This last finding was consistent with the more rapid development of inflammation in these strains than in the MRL/+ mice, where Lyt 2+ T suppressor/cytotoxic cells persist. Together, these results indicate that the autoimmune response in murine models of Sjögren's syndrome is a dynamic, evolving process with strain-related changes in lymphocyte subsets.