Before revision:  Results show that the model is remarkably robust against changes in the  kinetic parameters, noise levels, and mechanisms that activate T regulatory lymphocytes. In contrast, the model is extremely sensitive to changes in the ratio between T helper and T regulatory lymphocytes, exhibiting in particular a phase transition , from a responsive to an immuno-suppressed phase, when the ratio is lowered below a critical value .
After revision:  Results show that the model is remarkably robust against changes in the kinetic parameters, but it is very sensitive to changes in the ratio between T helper and T regulatory lymphocytes, exhibiting in particular a phase transition , from a responsive to an immuno-suppressed phase, when the ratio is lowered below a critical value .