D Antibodies are produced in an animal and then injected into a person. This is an artificially acquired passive immunity.

Artificially acquired passive immunity is a fascinating aspect of immunology. It involves transferring antibodies from another source to an individual. In this scenario, antibodies are produced in an animal and then injected into a person. This method is different from naturally acquired passive immunity, which happens, for example, when a mother passes antibodies to her baby through breast milk. The artificially acquired method is beneficial because it offers immediate protection against specific pathogens. However, unlike active immunity, which involves the body's own immune response, passive immunity does not last long. The introduced antibodies break down over time, and the individual won't have memory cells for long-term immunity.

Antibodies are crucial components of the immune system. They are proteins produced by B cells in response to antigens, which are foreign substances like bacteria or viruses. Antibodies have unique binding sites that match specific antigens. Once bound, they can neutralize the threat directly or tag the pathogen for destruction by other immune cells.

There are different types of antibodies, such as IgG, IgA, IgM, IgE, and IgD, each with a specific role in the immune response. For example, IgG is the most common antibody in blood and provides the majority of antibody-based immunity against pathogens.

The immune system is the body's defense mechanism against infections and diseases. It consists of various organs, cells, and proteins that work together to fight off harmful invaders.

Key components of the immune system include:

• White blood cells like lymphocytes (B cells and T cells) and phagocytes
• Antibodies
• The complement system
• The lymphatic system
• The spleen, thymus, and bone marrow

Each component has a unique role. B cells produce antibodies, while T cells destroy infected cells and regulate immune responses. Phagocytes engulf and digest pathogens, and the complement system helps antibodies and phagocytes clear microbes. The lymphatic system transports lymph, a fluid containing infection-fighting white blood cells. The spleen filters blood, the thymus is where T cells mature, and bone marrow produces new blood cells. The immune system must distinguish between self and non-self to function correctly, attacking only harmful invaders and not the body's own cells.