Periodically Pulsed Immunotherapy in a Mathematical Model of Tumor, CD4⁺ T Cells, and Antitumor Cytokine Interactions

Figure 11

The evolution of the fold-homoclinic bifurcation for , CD4⁺ T = 10. (a) A stable closed curve exists when IL-4 70. (b) A nonhyperbolic fixed point () appears on the curve IL-4 = 76.23, and the curve becomes homoclinic to . (c) splits into a saddle () and a stable node () when IL-4 76.23. All orbits are attracted to the curve under the map .

(a)

(b)

(c)