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 . To the best of our knowledge, this is the first mathematical study to support the validity of the T-helper/ T-regulator lymphocyte ratio as an index of immunosuppression , with a potential for prognostic monitoring .
After 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 , which is in line with experiments. This result supports the validity of the T-helper/ T-regulator lymphocyte ratio as an index of immunosuppression , with a potential for prognostic monitoring .