Principles of immunotherapy

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What is immunotherapy?

Immunotherapy is a form of cancer therapy that uses the innate or adaptive immune system of a patient to eradicate malignant cells. Although some variations of this therapy directly stimulate or disinhibit the patient’s own immune system, other variations of this therapy use immune cells manipulated ex vivo and introduce or reintroduce the cells back to the patient.

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How does the immune system interact with a tumor’s microenvironment in untreated patients?

In addition to unchecked cell division, development of a neovascular network, and accumulation of metastatic potential, a malignant tumor must evade the immune system to grow and thrive. Tumors achieve this immune evasion through a large array of mechanisms, but overcoming the resultant immune privilege within the tumor’s microenvironment (TME) is key to treating children with cancer.

Immune cells interact with cancer via immune surveillance, immune cell infiltration, and tumor cytolysis, allowing for three phases to occur: elimination, equilibrium, and esape. Immune surveillance is the process by which the immune system correctly recognizes cancer cells, leading to their ultimate destruction (elimination). Cancer cells can counteract this response by increasing markers of immune suppression or decreasing expression of surface markers that trigger immune responses (i.e. downregulating human leukocyte antigen [HLA] molecules, etc.). This can lead to an equilibrium where the tumor cells begin to become unrecognizable to the immune cells but there is still some control. Ultimately, escape occurs when the tumor cells overwhelm the immune system and can grow mostly unrestrained.

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