The human body has an elaborately developed immune system. The white blood cells, known as the “soldiers” of the immune system, are of two kinds. The first type of white blood cell, the phagocytes, acts as scavengers and non-specific destroyers of invaders. The second type, the T-lymphocytes or T-Cells, act more at the cellular level and are specific. The T-Cells mature in the Thymus gland. Under normal circumstances, T-Cells recognize an invader and employ a mechanism to destroy the foreign entity. T-Cells do not kill normal cells because of signals called “checkpoints.” The number of T-Cells and their normal functioning are crucial to immunity.
When a normal cell turns cancerous, they appear to put on an “invisible cloak or a force field,” which prevents the T-Cells from identifying and destroying these anomalies, thereby growing unchecked. Simply put, cancer cells dupe the immune system into thinking that they are harmless. This invisible cloak forms as a result of some cancer cells are sending out a checkpoint signal in order to avoid destruction by T-Cells. Scientists have identified this “checkpoint signal” and have designed inhibitors for this so that the cloak is removed, and T-Cells will have access to the abnormal cancer cells. New drugs called “checkpoint inhibitors” or “checkpoint blockade antibodies” are used for the purpose of getting the T-cells in the “attack mode” again. This type of treatment is called “checkpoint blockade immunotherapy.”
Some clinical trials have been conducted with checkpoint blockade immunotherapy for various types of cancer, and the results appear to be promising. Conventional chemotherapy for cancers can have severe side effects and may stop working over time. In contrast, the side effects of this kind of immunotherapy seem milder in the patients tested so far. Further studies will be required for long-term effects of immunotherapy for cancer, in terms of how long a patient is healthy between treatments and if the therapy stops working after a certain period. However, the good news is that innovative treatments are available for different types of cancer and should be actively considered.
Written by Mangala Sarkar Ph.D.