Biology – The immune system | e-Consult

Self antigens are molecules that are naturally present in the body's own cells and tissues. They are a normal part of the body's composition and are not recognized as foreign. Non-self antigens, on the other hand, are molecules that originate from outside the body, such as those found on pathogens (bacteria, viruses, fungi, parasites) or foreign substances (e.g., pollen, transplanted tissues).

The immune system *must* be able to distinguish between self and non-self antigens to avoid attacking the body's own tissues. If the immune system mistakenly attacks self antigens, it leads to autoimmune diseases, where the body's immune response is directed against its own cells and organs. This can cause a wide range of health problems, from rheumatoid arthritis to type 1 diabetes. Therefore, a critical function of the immune system is to develop mechanisms to tolerate self antigens and mount an effective response only against non-self antigens.