Bifurcation analysis for a nonlinear system of integro-differential equations modelling tumor-immune cells competition

A bifurcation analysis is developed for the initial value problem for a non linear system of integro-differential equations modelling the competition b etween tumor cells and immune system. It is shown that there exists a criti cal value of a bifurcation parameter separating situations where the immune system controls the neoplastic growth from those where tumor growth is not contrasted. This result refers to conjecture that the action of cytokine s ignals can modify the outputs of the competition. (C) 1998 Elsevier Science Ltd. All rights reserved.