The basic prerequisite for the immune system to become active is adequate information on the target cells which are to be destroyed. Therefore, it has special information cells (antigen presenting cells) that function as sentinels. The most important representatives of this cell class are called dendritic cells. They ingest components of malignant or infected cells (so called antigen) and present them to lymphocytes. This contact causes the lymphocytes to differentiate into killer cells (effector cells) that can attach malignant cells anywhere in the body. A part of these lymphocytes become memory cells that maintain enduring immune response against cancer cells.

To sum up, the most important precondition for the immune system to fight tumour cells is specific information. Only through ‘antigen presentation’, the lymphocytes can recognize and destroy the tumour cells as well as develop a lasting immune response.