Eqs 1–12 are applied in the following discussion with the parameters given in Table A in S1 File. The time course of the simulations is marked in days and units of cell populations and cytokine concentrations are in terms of cells per milliliter (cells/ml) and pmol per liter (pmol/L). The initial conditions of the variables for all activated cells and secreted cytokines are set to zero. CS-induced immune response and COPD progression are dependent upon the dose of CS inhalation . Figs 2–4 respectively show the time courses of the changes in the immune cells, cytokines and tissue damage (TD) in response to CS at a relatively high level of the cigarette smoking intensity, S (S = 1.67). Here, S is defined as the ratio of a CS dose to the minimal CS dose required to cause COPD with the parameters given in Table A in S1 File.