Host-guest interaction in cancer and a reason for the poor efficiency of the immune system in its detection and termination

Organisms (like amoebae, bacteria, etc.), whose population in an unlimited nutritive medium would grow exponentially with time, behave often as aggressive strain with respect to higher organisms. Higher organisms provide a medium very different from the unlimited one considered above; among the various niches where the strain growth is possible, the circulatory system plays a special role. The topological structure of the circulatory system (two interlocked trees addressed to the delivery of O2 and nutritive substances to all tissues forming the higher organism and to the elimination of metabolic wastes) poses constraints to the growth of the strain population. The immune system is devoted to control and eventually to terminate the strain growing inside the organism. In many cases the immune system is sufficiently effective for that; there is a case, however, for which the immune system generally fails—cancer. In this work, after considering a few elementary properties of the growth of strains and higher organisms, I shall consider how the structure of the latter affects the population dynamics of cancer, and identify a possible reason why the immune system is so ineffective in recognizing cancer cells.