Objective: To assess the association of CD40/CD40 ligand (CD40L) interactions with the development of skin fibrosis and autoimmunity in tight-skin (TSK/+) mouse, which is a mouse model for human systemic sclerosis.
Methods: Newly born TSK/+ mice were treated by murine anti-CD40L monoclonal antibody (Ab, 100 μg i.p. weekly). Hypodermal thickness of 8-week-old female mice, which was defined as the thickness of a subcutaneous loose connective tissue layer beneath the panniculus carnosus, was measured under a light microscope. All skin sections were taken from the para-midline, upper back region. Serum anti-topoisomerase I autoantibody levels, serum immunoglobulin levels, and plasma soluble CD40L levels were determined by enzyme linked immunosorbent assay. For analysis of lymphocytes surface molecules, single-cell suspensions of lymphocytes were stained by monoclonal Abs. Proliferation of TSK/+ B cells and fibroblasts to anti-CD40 Ab was assessed by the uptake of [3H]-labeled thymidine and BrdU, respectively.
Results: The blockade of CD40/CD40L interactions by anti-CD40L monoclonal Ab significantly reduced cutaneous fibrosis (65%) and anti-topisomerase I autoantibody in TSK/+ mice. Anti-CD40L monoclonal Ab also normalized B lymphocyte abnormal activation in TSK/+ mice, demonstrated by hyper-γ-globulinemia. Furthermore, augmented CD40/CD40L interactions in TSK/+ mice were suggested by up-regulated expression of CD40L on CD4+ T cells, elevated plasma soluble CD40L levels. The hyperresponsiveness to CD40 stimulation was also observed in TSK/+ B cells and fibroblasts.
Conclusion: Cutaneous fibrosis and autoimmunity in TSK/+ mice are closely correlated with CD40/CD40L interactions
- systemic sclerosis