Final answer:
The healthy human immune system does not react to a) self antigens. This lack of reaction, known as immune tolerance, is key to preventing autoimmune diseases and maintaining the body's harmony.
Step-by-step explanation:
A healthy human immune system does not react to a) self antigens.
When the immune system identifies a molecule as a self antigen, it does not provoke an immune response against it. This is crucial for maintaining the body's internal harmony and preventing autoimmune diseases. In contrast, non-self antigens, which may be found on pathogens like bacteria and viruses, elicit an adaptive immune response, which includes the production of antibodies.
Molecules classified as self are typically a normal part of the body's own cells and tissues. Recognition of self antigens by immune cells is mediated by Major Histocompatibility Complex (MHC) molecules, which help prevent the immune system from attacking the body's own cells. This state of non-responsiveness to self is known as immune tolerance. Autoimmune diseases can occur when this tolerance is disrupted and the immune system mistakenly targets self antigens.