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Fig. 2 | BMC Evolutionary Biology

Fig. 2

From: Coevolutionary feedback elevates constitutive immune defence: a protein network model

Fig. 2

Immune effector activity and corresponding network architecture. A host expresses a fixed level of constitutive effector activity (green box; \(y^{0}_{\mathrm {E_{S}}}\) and \(y^{0}_{\mathrm {E_{N}}}\) in Eqs. 3 and 4) throughout its lifetime, enabled by the interactions between the constitutively active protein (C) and the effectors (ES and EN). The induced effector activity (blue box) is defined as the difference between the effector activity following the parasite-receptor interaction (\(y^{*}_{\mathrm {E_{S}}}\) and \(y^{*}_{\mathrm {E_{N}}}\) in Eqs. 5 and 6) and the constitutive activity. This additional activity is triggered when a parasite (P) is detected by the receptor (R). A time delay is assumed between encountering a parasite and triggering the induced response. Both the cost and benefit of defence are realised as a function of the effector activity (Eqs. 36)

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