The Immune System Overview

The body's complex defense mechanism that protects against harmful agents such as bacteria, viruses, and toxins.

The ability of the immune system to distinguish between the body's own cells and foreign substances.

Any substance that triggers an immune response. It can be a molecule, a protein, or a fragment of an invading organism.

The first line of defense of the immune system. It is the body's natural defense mechanism against invaders.

The second line of defense of the immune system. It is more specific and can target particular invaders.

The process by which the adaptive immune system remembers previous encounters with specific antigens.

Cells of the adaptive immune system responsible for attacking and destroying specific antigens.

The ability of the adaptive immune system to react faster and more efficiently to a second exposure to the same antigen.

Immune system response where antibodies are produced by B lymphocytes to neutralize pathogens.

Immune system response where T lymphocytes directly attack infected cells or pathogens.

The stage where B cells haven't encountered an antigen yet, meaning they haven't learned to recognize a specific pathogen.

The process of B cells maturing into plasma cells after encountering an antigen. Plasma cells are antibody factories.

Specialized proteins produced by plasma cells, capable of recognizing and binding to specific antigens.

The primary function of humoral immunity is to protect against extracellular pathogens, which are outside of cells.

The primary function of cell-mediated immunity is to target intracellular pathogens, which live within host cells.

T lymphocytes mature in the thymus, a gland located in the chest.

Immature B cells mature in the bone marrow, spleen, and lymph nodes.

Mature T cells are found circulating in the bloodstream and residing in lymph nodes.

Antigen fragments are displayed on the surface of antigen-presenting cells (APCs) to activate cytotoxic T cells (CD8+). These cells then destroy infected cells via apoptosis.

A weakened or inactivated form of a virus that cannot cause disease. It contains the genes for the disease but is unable to replicate in the body.

A repeated dose of a vaccine given some time after the initial dose. It serves as a reminder to the body to produce more antibodies.

Tests that measure the levels of specific antibodies (IgM and IgG) in the blood. They are used to determine if a person has been exposed to a particular antigen and has developed immunity.

Specific proteins produced by the immune system that recognize and bind to particular antigens, triggering an immune response.

A type of immunoglobulin that is the most abundant in blood serum and plays a key role in fighting infections.

A type of immunoglobulin found primarily in mucosal secretions (e.g., saliva, tears, breast milk) and provides localized protection against pathogens.

A type of immunoglobulin associated with allergic reactions and parasitic infections.

A type of immunoglobulin found primarily in the blood during early immune responses and can activate the complement system.

A type of immunoglobulin found on B cells and involved in antibody production and immune regulation.

A type of immune response acquired through exposure to an antigen or vaccination.

A type of immune response where pre-made antibodies are provided to an individual either through injection or passively transferred from a mother to her baby.

A type of cell that presents antigens to T cells, triggering the activation of the immune response.