Immune escape is one of the hallmarks of cancer development and metastasis. It is characterized by the lack of ability of the immune system to eliminate transformed cells prior to and after tumor development.
Several mechanisms have been proposed and tested to explain cancer immune escape. It is now evident that both the host as well as the tumor play important roles in this phenomenon. The host’s contribution is manifested by the host’s ability to recognize to antigens expressed by tumor cells, a phenomenon known as “host ignorance.” It happens because of defects in both the innate and adaptive arms of the immune system. The tumor’s contribution is manifested by the adaptation of tumor cells to evade the immune systems or developing a microenvironment that suppresses the immune system.