Effects of immunomodulating treatment on autoimmune sialadenitis in MRL/Mp-lpr/lpr mice

The autoimmune MRL/Mp-lpr/lpr (MRL/l) mouse spontaneously develops sialadenitis with a morphological and phenotypical pattern similar to that seen in human Sjögren's syndrome (SS). This makes the MRL/l mouse a suitable model for therapeutical studies of autoimmune sialadenitis. We have, by histological and immunohistochemical techniques, analyzed the therapeutical effect of treatment with LS2616, a recently synthesized oxokinolinamide derivative, on sialadenitis in submandibular glands of MRL/l mice. The results were compared with effects obtained after treatment with cyclophosphamide (CY) and physiologic saline. Administration of both LS2616 and CY to MRL/l mice has previously been found to result in prolongation of survival and amelioration of organ pathology. However, only CY treatment reduced sialadenitis, while LS2616 increased the semiquantitatively assessed focal inflammation of salivary glands in 6 months old mice. No differences in T-cell phenotypes of infiltrating lymphoid cells in salivary glands between different treatment regims could be noted. However, the frequency of B-cells in the sialadenitis was decreased in the CY treated group. In contrast, CY but not LS2616 treatment normalized expression of T-helper and cytotoxic T-cell phenotypes as well as reduced the B-cell portion in lymph nodes. It is concluded that CY treatment can suppress sialadenitis although both LS2616 and CY are effective in prolongation lifespan of MRL/l mice. This may implicate different immunopathogenic mechanisms for development of sialadenitis versus other organ lesions in the autoimmune disease of MRL/l mice.