BioModels

We present a novel mathematical model involving various immune cell populations and tumor cellpopulations. The model describes how tumor cells evolve and survive the brief encounter with theimmune system mediated by natural killer (NK) cells and the activated CD8þcytotoxic T lymphocytes(CTLs). The model is composed of ordinary differential equations describing the interactions betweenthese important immune lymphocytes and various tumor cell populations. Based on up-to-dateknowledge of immune evasion and rational considerations, the model is designed to illustrate how tu-mors evade both arms of host immunity (i.e.innate and adaptive immunity). The model predicts that(a) an influx of an external source of NK cells might play a crucial role in enhancing NK-cell immunesurveillance; (b) the host immune system alone is not fully effective against progression of tumor cells;(c) the development of immunoresistance by tumor cells is inevitable in tumor immune surveillance. Ourmodel also supports the importance of infiltrating NK cells in tumor immune surveillance, which can beenhanced by NK cell-based immunotherapeutic approaches.