Dr Simon Naylar, a pathologist, helps us get a better understanding of biomarkers in relation to immunotherapy. Understanding the immune system The immune system is a finely-tuned balanced harmony of cells and molecules ready to react to the threat posed to the body by infections, foreign entities and tumours.  Once the immune system detects one of these potential threats (known as an antigen), the immune defences are activated and a complex set of reactions and responses begin the process of attacking this enemy.  Many tumour cells are destroyed by the immune cells and the action of antibodies (proteins which attack foreign cells or molecules). Immunotherapy explained…