Biology · Ch 7 — Human Health and Disease
Auto Immunity
Auto Immunity
The Basis of Immunity: Self vs. Non-self
The immune system of higher vertebrates — including humans — has a remarkable ability: it can tell the difference between the body's own cells (self) and foreign invaders (non-self), such as bacteria, viruses, or fungi. This ability to discriminate is the foundation of acquired immunity, which is also called memory-based immunity because it "remembers" past infections.
Exactly how the body makes this distinction is still not fully understood. However, two important consequences of this ability are well established.
Two Key Consequences of Self–Non-self Discrimination
1. Recognition of foreign molecules, not just whole organisms
The immune system does not only recognise entire foreign organisms. It can also identify individual foreign molecules — for example, a protein on the surface of a virus or a toxin released by a bacterium. Most experimental immunology research focuses on this aspect: how the body detects and responds to these molecular markers, called antigens.
2. Autoimmunity — when the body attacks itself
Sometimes, due to genetic factors or other unknown reasons, the immune system loses its ability to distinguish self from non-self. In such cases, it begins to attack the body's own cells and tissues. This misguided attack causes damage to the body and is called an auto-immune disease.
A common misconception
Auto-immune diseases are not infections. The body is not fighting an outside invader — it is mistakenly attacking its own healthy cells.