Fig 3. Simulated population dynamics of epithelial cells, immune effectors and bacteria in chlamydia infections.

In A, the immune cell proliferation is rapid, which leads to an acute infection. In B and C, immune cells do not proliferate fast enough to clear the bacteria and the acute phase is followed by oscillations and the establishment of a chronic phase (plateau of EB density). The infection is lytic reducing the thickness of the epithelium (A, B and C) but only chronic infections manage to infect the lower layers (B and C). Parameter values are default (Table 3 and literature values in Table 1) except in A where β_b = 8.0 × 10⁻⁷ cell⁻¹⋅ EB⁻¹⋅ day⁻¹, β_p = 4.0 × 10⁻⁶ cell⁻¹⋅ EB⁻¹⋅ day⁻¹, β_u = 2.0 × 10⁻⁵ cell⁻¹⋅ EB⁻¹⋅ day⁻¹, and φ = 0.0015 day⁻¹. In C, all four epithelial protective measures happen together, i.e. ζ_u, ρ_b, μ, and ν all rise logistically to a threshold above default after infection to mimic the protective epithelial response (see section A.3 S1 Text, eqn 7a with θ = 1). Thresholds used in C: ${\zeta }_{u_{max}}=6{\text{day}}^{-1}$, ${\rho }_{b_{max}}=0.3{\text{day}}^{-1}$, μ_max = 0.9 cell⁻¹⋅ day⁻¹, and ν_max = 0.8 day⁻¹.