mTORC1 Inhibition Protects Human Regulatory T Cells From Granzyme-B-Induced Apoptosis.

Regulatory T cells (Tregs) have shown great promise as a means of cellular therapy in a multitude of allo- and auto-immune diseases-due in part to their immunosuppressive potency. Nevertheless, the clinical efficacy of human Tregs in patients has been limited by their poor in vivo homeostasis. To avert apoptosis, Tregs require stable antigenic (CD3ζ/T-cell-receptor-mediated), co-stimulatory (CD28-driven), and cytokine (IL-2-dependent) signaling. Notably, this sequence of signals supports an activated Treg phenotype that includes a high expression of granzymes, particularly granzyme B (GrB). Previously, we have shown that aside from the functional effects of GrB in lysing target cells to modulate allo-immunity, GrB can leak out of the intracellular lysosomal granules of host Tregs, initiating pro-apoptotic pathways. Here, we assessed the role of inhibiting mechanistic target of rapamycin complex 1 (mTORC1), a recently favored drug target in the transplant field, in regulating human Treg apoptosis via GrB. Using ex vivo models of human Treg culture and a humanized mouse model of human skin allotransplantation, we found that by inhibiting mTORC1 using rapamycin, intracytoplasmic expression and functionality of GrB diminished in host Tregs; lowering human Treg apoptosis by in part decreasing the phosphorylation of S6K and c-Jun. These findings support the already clinically validated effects of mTORC1 inhibition in patients, most notably their stabilization of Treg bioactivity and in vivo homeostasis.

Plasmapheresis rescue therapy in progressive systemic ANCA-associated vasculitis: single-center results of stepwise escalation of immunosuppression.

OBJECTIVE: We evaluated 26 patients with antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) with progressive disease despite treatment with cyclophosphamide and steroids treated with additional plasmapheresis and compared outcome with 50 matched-disease controls. METHODS: Patients diagnosed with AAV and treated with cyclophosphamide from January 1990 to December 2009 (n = 272) were included when plasmapheresis was not started at diagnosis but added for progressive disease during initial standard therapy (n = 26). We selected controls equal for age, Birmingham vasculitis activity score, and creatinine at diagnosis. Primary endpoint was estimated glomerular filtration rate (eGFR) or death. RESULTS: Plasmapheresis was added 18 days (range 5-41) after start of therapy. In 11 patients, a rise in serum creatinine >30% led to plasmapheresis; insufficient response to induction (n = 11), progressive pulmonary disease (n = 3), or progressive necrotic lesions (n = 1) were other indications.In the plasmapheresis group, six patients were in need of renal replacement therapy (RRT), and three controls. Five years after diagnosis, four patients had died in the plasmapheresis against eight controls (P = 0.94). At baseline, mean eGFR was 44 ml/min/1.73 m(2) in plasmapheresis group versus 43 ml/min/1.73 m(2) in controls. At start of plasmapheresis, eGFR was 26 ml/min/1.73 m(2) (P = 0.003), at 6 months mean eGFR had significantly improved to 44 ml/min/1.73 m(2) (P = 0.0003), comparable to eGFR in controls, 48 ml/min/1.73 m(2). During long-term follow-up, there was no difference in renal function between the groups. CONCLUSION: AAV patients with progressive disease despite standard induction therapy in whom plasmapheresis was added had significant improvement in renal function and similar long-term outcome in both renal and patient survival as matched disease controls.

Pauci-immune necrotizing glomerulonephritis.

Pauci-immune necrotizing glomerulonephritis is the most frequent cause of rapidly progressive glomerulonephritis and, in most cases, is associated with antineutrophil cytoplasmic antibodies (ANCA). It is either the renal manifestation of Wegener's granulomatosis, microscopic polyangiitis of Churg-Strauss syndrome, or a renal-limited vasculitis. In this review, the histopathologic changes seen in renal biopsies of patients with pauci-immune glomerulonephritis are described. The authors also describe why the disease is sometimes limited to the kidneys, the clinical course of renal disease, treatment issues, how to deal with disease relapses, and how to prevent them from occurring. Furthermore, the necessity of renal biopsy and rebiopsy, the usefulness of rapid ANCA detection at diagnosis, and serial measurement of ANCA during follow-up are discussed. The effect of dialysis on the disease process and the possibility of renal transplantation after disease remission are also debated.