A novel costimulation pathway via the 4C8 antigen for the induction of CD4+ regulatory T cells.

CD4(+)CD25(+) regulatory T (Treg) cells naturally occur in mice and humans, and similar Treg cells can be induced in vivo and in vitro. However, the molecular mechanisms that mediate the generation of these Treg cell populations remain unknown. We previously described anti-4C8 mAbs that inhibit the postadhesive transendothelial migration of T cells through human endothelial cell monolayers. We demonstrate in this work that Treg cells are induced by costimulation of CD4(+) T cells with anti-CD3 plus anti-4C8. The costimulation induced full activation of CD4(+) T cells with high levels of IL-2 production and cellular expansion that were comparable to those obtained on costimulation by CD28. However, upon restimulation, 4C8-costimulated cells produced high levels of IL-10 but no IL-2 or IL-4, and maintained high expression levels of CD25 and intracellular CD152, as compared to CD28-costimulated cells. The former cells showed hyporesponsiveness to anti-CD3 stimulation and suppressed the activation of bystander T cells depending on cell contact but not IL-10 or TGF-beta. The suppressor cells developed from CD4(+)CD25(-)CD45RO(+) cells. The results suggest that 4C8 costimulation induces the generation of Treg cells that share phenotypic and functional features with CD4(+)CD25(+) T cells, and that CD25(-) memory T cells may differentiate into certain Treg cell subsets in the periphery.

Effects of FTY720 in MRL-lpr/lpr mice: therapeutic potential in systemic lupus erythematosus.

UNLABELLED: OBJECTIVE To examine the effects of a novel immunosuppressant, FTY720, on hematolymphoid cells and the clinical course of MRL-lpr/lpr (MRL/lpr) mice genetically predisposed to systemic lupus erythematosus (SLE). METHODS: Apoptosis of hematolymphoid cells was determined in vitro by FACScan after staining with propidium iodide or merocyanine 540. From 4 months of age, 15 female MRL/lpr mice received oral administration of 2 mg/kg each of FTY720, methylprednisolone (mPSL), or vehicle, 3 times per week. Therapeutic efficacy was evaluated by levels of anti-dsDNA antibodies in serum and the survival rate. In parallel, T cell proliferation and secretion of interleukin 2 (IL-2) induced by anti-CD3, phenotypes of the spleen, lymph node and bone marrow cells, as well as immunohistochemistry of the kidney, were examined in vitro. RESULTS: FTY720 at 2 microM induced apoptosis in more than 70% of double negative (CD4-/CD8-) T cells from the spleen of MRL/lpr mice in vitro. Oral FTY720 was tolerated well with no apparent side effects. FTY720 treated and control mice gained weight at an identical pace through to 9 months of age. FTY720 significantly suppressed the production of anti-dsDNA antibodies (FTY720 vs control: 1739 +/- 898 U/ml vs 410 +/- 356 U/ml at 8 months of age; p < 0.05) and reduced the deposition of IgG in glomeruli compared to control animals. At 9 months of age, the survival rate in the FTY720 treated mice was 86.9% compared to 33.0% in controls (p < 0.01). FTY720 decreased the number of double negative T cells from the spleen and lymph nodes in vivo, and increased T cell proliferation and IL-2 secretion induced by anti-CD3 stimulation in vitro. CONCLUSION: FTY720 suppressed the development of autoimmunity and prolonged the lifespan of female MRL/lpr mice. Suppression of autoimmunity, at least in part, may have resulted from an apoptogenic potential of FTY720. Hence, it could be useful for primary or adjunctive therapy of human SLE.