|M.Sc Student||Eiza Nasren|
|Subject||Fas-Ligand high CD5 high expressing B cells: association|
with increased viral load and autoimmunity in
patients with chronic hepatitis C virus
|Department||Department of Medicine||Supervisors||? 42? Elias Toubi|
|Clinical Professor Zahava Vadasz|
|Full Thesis text|
B regulatory cells (Breg) are recognized as a wide spectrum of B cells, characterized by various membrane markers, and by expressing or secreting inhibitory cytokines. Their main role is to maintain self-tolerance and to prevent autoimmune diseases. In recent years, attention is directed to a new subset of Breg cells characterized by expressing Fas-Ligand (FasL) and therefore is called "killer" B cells. They are CD5highFasLhigh and IL-10 producing B cells, and are reported to play role mainly in suppressing anti-viral and anti-tumor immune responses.
In this study, we try to characterize this subset of cells, namely, to assess their role in chronic hepatitis C virus (HCV) infection and to see if they possibly contribute to the increased viral load and persistence of HCV. In this case, primary and activated B cells were assessed, focusing on the difference between CD19?? and CD19?? cells. Next, we studied the potential of these killer B cells (CD5highFasLhigh) to induce CD4 and CD8 T cell apoptosis. We also asked to prove that killing of CD4 and CD8 T cells is FasL dependent and that increased FasL expression on these cells is in association with increased viral load and autoimmunity.
Our main findings in this study are:
1. FasL expression on CD5high B cells is significantly increased in HCV infected patients compared to that in healthy individuals (28.06±6.71 MFI vs. 10.87±3.97 MFI, P<0.0001, respectively).
2. The FasLhiCD5hi expressing B cells is significantly higher in HCV infected patients compared to healthy individuals (44%±15.95% vs. 29.46%±12.58%, P <0.0001, respectively).
3. Killer B cells from HCV patients induce increased autologous CD4 T cell apoptosis when compared to that of healthy individuals (39.17%±7.18% vs. 25.92%±8.65%, p<0.0001, respectively). A similar increase was observed in CD8 T cell apoptosis (54.67%±15.49% vs. 21.07%±7.4%, p<0.0001, respectively).
4. We were able to show that the induction of apoptosis by killer B cells is FasL dependent by neutralizing this with monoclonal anti-FasL antibodies.
5. Increased expression of FasL on CD5high B cells is in positive correlation with increased viral load and the presence of autoantibodies- Anti-nuclear antibodies and Rheumatoid Factor in HCV (r=0.55, r=0.42, r=0.41, p<0.01, respectively).
This is the first study were "killer" B cells are found to play a pathogenic role in HCV. Together with other cytotoxic cells (cytotoxic T cells and CD4 effector T cells), they are involved in the ability of HCV to escape efficient immune responses and persist both in peripheral blood and in the liver.