Final answer:
Immunity is the body's ability to ward off infections, with innate immunity being present from birth and adaptive immunity developing after exposure to antigens. Critical components of the immune system include lymphocytes, interferon, macrophages, and MHC molecules, which facilitate the recognition and neutralization of pathogens. Active and passive immunity represents how the body acquires its protective responses.
Step-by-step explanation:
Immunity is the biological term for the body's ability to resist pathogens, such as viruses and bacteria, which can lead to infections. Humans have different types of immunity, including innate immunity and adaptive immunity. Innate immunity is present from birth and is not caused by previous infection or vaccination. It includes physical barriers such as skin and also encompasses cellular components like macrophages and various cytokines like interferon, which help inhibit viral replication.
On the other hand, adaptive immunity is acquired over time and involves a more specific response. This form develops after exposure to antigens through processes such as vaccination or previous infection, leading to the formation of memory cells like B and T lymphocytes. The major histocompatibility complex (MHC) I and II molecules play a crucial role in the adaptive immune system's ability to distinguish between self and non-self cells, providing a mechanism for the immune system to recognize and respond to infected or cancerous cells.
The immune system is a complex network of cells, proteins, and other components that protect the body against infection. Substances that the immune system recognizes as foreign and potentially harmful are known as antigens, and they can trigger an immune response that includes the production of antibodies, also referred to as immunoglobulins. This protective mechanism is known as the body's defense mechanism.