Before revision:  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:  In contrast, the model is extremely sensitive to changes in the ratio between T-helper and T-suppressor lymphocytes, exhibiting in particular a phase transition , from a responsive to an immuno-suppressed phase, when the ratio is lowered below a critical value .