Antibody-mediated immunity

Antibody-Mediated Immunity

Antibody-mediated immunity, also known as humoral immunity, is a type of immune response that involves the production of antibodies by B cells in response to an antigen. This form of immunity is critical for the body's defense against pathogens, particularly bacteria and viruses that are extracellular (outside cells).

Overview

When an antigen enters the body, it is recognized by antigen-presenting cells (APCs), such as dendritic cells and macrophages. These cells engulf the antigen, process it, and present fragments of it on their surface using major histocompatibility complex (MHC) molecules.

B cells, a type of white blood cell, recognize these antigen fragments through their B cell receptors (BCRs). This interaction, along with signals from helper T cells, stimulates the B cells to differentiate into plasma cells and memory B cells.

Plasma cells are the body's antibody factories. They produce and secrete large amounts of antibodies that are specific to the antigen. These antibodies circulate in the bloodstream and lymphatic system, binding to the antigen wherever it is found. This marks the antigen for destruction by other immune cells, such as phagocytes.

Memory B cells, on the other hand, do not produce antibodies immediately. Instead, they remain in the body long-term and provide a rapid response if the same antigen is encountered again.

Types of Antibodies

There are five main types of antibodies, also known as immunoglobulins: IgG, IgA, IgM, IgD, and IgE. Each has a different role in the immune response. For example, IgG antibodies are the most common and are involved in the majority of immune responses, while IgE antibodies are involved in allergic reactions.

Clinical Significance

Antibody-mediated immunity is crucial for protection against many infectious diseases. Vaccines work by stimulating this type of immune response, leading to the production of memory B cells and antibodies that can provide long-term protection.

However, problems with antibody-mediated immunity can lead to disease. For example, autoimmune diseases occur when the immune system produces antibodies against the body's own tissues. Additionally, some individuals may have immunodeficiency conditions that impair their ability to produce antibodies, making them more susceptible to infections.

See Also

• Cell-mediated immunity
• Immune system
• Vaccine
• Autoimmune disease
• Immunodeficiency