 In this work we use a combination of statistical physics and dynamical systems approaches , to analyze the  response to an antigen  of a simplified model of the adaptive immune system, which comprises B, T helper and T regulatory lymphocytes. 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 . 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 .
Recent experimental studies have suggested the ratio between T-helper and T-suppressor lymphocytes as an index of immunosuppression in HIV, cancer, immunosenescence and inflammatory and auto-immune diseases. However, a quantitative understanding of the impact of this ratio on the immune response has lagged behind data and its validity as a tool for prognostic monitoring or therapeutic target remains an open question. In this work , we use statistical physics and dynamical systems approaches to analyze the time-dependent response to an antigen , of a simplified model of the adaptive immune system, which comprises B, T-helper and T-suppressor lymphocytes. The model is remarkably robust against changes in the noise level and kinetic parameters, but it is very sensitive to changes in the ratio between T-helper and T-suppressor lymphocytes, exhibiting , in particular, a transition from a responsive to an immuno-suppressed phase, as the ratio is lowered below a critical value , which is in line with experiments. This result supports the validity of the T-helper/ T-suppressor ratio as an index of immunosuppression and may provide a useful theoretical benchmark to interpret and compare experiments .
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Recent experimental studies have suggested the ratio between T-helper and T-suppressor lymphocytes as an index of immunosuppression in HIV, cancer, immunosenescence and inflammatory and auto-immune diseases. However, a quantitative understanding of the impact of this ratio on the immune response has lagged behind data and its validity as a tool for prognostic monitoring or therapeutic target remains an open question.
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time-dependent
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T helper and T regulatory lymphocytes. Results show that the
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noise level and
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noise levels, and mechanisms that activate T regulatory lymphocytes. In contrast, the model is extremely
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T helper and T regulatory
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in particular a phase transition ,
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. To the best of our knowledge, this is the first mathematical study to support the
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, with a potential for prognostic monitoring
and may provide a useful theoretical benchmark to interpret and compare experiments