טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentStroopinsky Dina
SubjectInduced T Cells as a Potential Therapy for Graft-Versus-
Host Disease
DepartmentDepartment of Medicine
Supervisor Professor Emeritus Jacob Rowe
Full Thesis textFull thesis text - English Version


Abstract

It was demonstrated that CD4+CD25+ naturally occurring regulatory T cells (nTregs) play a crucial role in mediating tolerance following allogeneic transplantation and may prevent the development of Graft versus Host Disease (GvHD).  As such, nTregs are being explored as a therapeutic tool for GvHD prevention or treatment.  These cells demonstrate a nonspecific immune suppression; therefore their use is potentially complicated by an associated increased risk of infection and post-transplant tumor progression. The generation of immunosuppressive population that selectively inhibits GvHD without adversely effecting post-transplant immune reconstitution and anti-tumor immunity remains a challenge for improving outcomes following allogeneic transplantation.

  Induced CD4+CD25+ T cells have been shown to express the main regulatory gene FOXP3, similar to nTregs. However, the suppressive capacity of these cells is under debate. The current study was designed to investigate the functional characteristics of induced CD25+FOXP3+ derived from CD25- cells. Allogeneic stimulation of CD25- PBMCs resulted in production of CD4+CD25high cells. The resultant population has concurrently exhibited regulatory markers and inflammatory cytokines (IL-2 and IFN-γ). These induced FOXP3+IFN-γ+ T cells were shown, for the first time, to markedly inhibit alloreactive T-cell expansion. However, in contrast to nTregs, the induced CD4+CD25+FOXP3+ cells did not suppress proliferation against third party stimulator and cytomegalovirus, suggesting a more selective suppressive capacity targeted against original stimulus only.

The current study has also shown that stimulation of CD25- T cells with allo-DCs generated a large fraction of induced CD8+CD25+FOXP3+ T cells. These cells exhibited a mixed phenotype demonstrating expression of regulatory markers, as well as indicators of effector properties such as granzyme B and production of Th-1 cytokines following both mitogenic and antigen specific stimulations. Similar to induced CD4+CD25+ T cells, the CD8+CD25+ population markedly selectively inhibited allo-reactive T-cell expansion.

Another approach for GvHD treatment, investigated in the present study, was a direct inactivation of allo-reactive T cells which was not mediated through suprresive cells.

Rituximab is a chimeric anti-C20 monoclonal antibody, being used for B cell malignancies and autoimmune disorders. We demonstrate that rituximab induced a dose-dependent reduction in activation markers, inflammatory cytokines and proliferative capacity upon in-vitro stimulation. These phenomena were also demonstrated in 8 patients with B-cell lymphoma following rituximab therapy. The production IL-2 and IFN-γ by T cells was significantly decreased within hours post rituximab. Rituximab was shown to inactivate T cells directly; therefore further studies are warranted in order to use it in GvHD treatment.