Immunity is defined as what?

Immunity is fundamentally the body's ability to recognize foreign substances, such as pathogens like bacteria and viruses, and respond to them effectively. This definition encompasses the mechanisms through which the immune system identifies these foreign invaders and neutralizes their potential threat to health.

Understanding immunity involves key concepts such as the recognition of antigens (substances that provoke an immune response), activation of immune cells, and the production of antibodies that target these foreign materials. This capacity is essential for maintaining health and protecting the body from infections and diseases.

The other options do not accurately reflect the definition of immunity. Developing allergies relates to inappropriate immune responses where the body reacts to harmless substances. Susceptibility to diseases describes a vulnerability rather than an active protective response. The tendency to accumulate toxins does not pertain to the immune system's role but rather to biochemical and physiological processes in the body. Thus, the correct choice relates precisely to the immune system's primary function of recognizing and neutralizing foreign materials.