The Immune System Overview

Immunity acquired by the body's own immune response to a pathogen. This results in the production of memory cells that provide lasting protection.

Immunity gained by receiving antibodies from another source, rather than producing them yourself. This is short-lived.

Type of active immunity where the body naturally encounters a pathogen, develops symptoms, and then builds immunity. Example: recovering from chickenpox.

Type of active immunity where a weakened or inactivated form of a pathogen is introduced, triggering the immune response. Example: Vaccination.

Type of passive immunity where antibodies are transferred from mother to child during pregnancy or breastfeeding.

Type of passive immunity where antibodies are injected into a person to provide immediate, but temporary protection. Example: Antivenom.

The body's initial and non-specific defense system against pathogens. It acts as the first line of defense and does not provide long-lasting immunity.

A rapid response to injury or infection, characterized by redness, heat, swelling, and pain. It's a sign that the immune system is working to fight off pathogens.

Immune proteins that work in a cascade to destroy pathogens by enhancing antibody and phagocyte function, promoting inflammation, and attacking the pathogen's membrane.

The most abundant white blood cells, crucial for early defense against bacterial infections. They engulf and destroy pathogens through phagocytosis.

White blood cells involved in fighting parasitic infections and allergic reactions.

White blood cells that release histamine and other mediators, contributing to inflammation and allergic responses.

Phagocytic cells that engulf and digest pathogens and dead cells. They also present antigens to T cells to initiate adaptive immunity.

Antigen-presenting cells (APCs) that capture antigens and present them to T cells, initiating the adaptive immune response.

A fluid containing immune cells, circulating throughout the body. It plays a critical role in filtering pathogens and facilitating immune responses.

T cells mature in the thymus gland.

B cell deficiency causes reduced antibody production, leaving the body vulnerable to extracellular pathogens like bacteria and viruses. These infections often manifest as recurrent respiratory problems.

Recurrent bacterial infections in a child, especially affecting the respiratory system, could indicate a B cell deficiency.

Organ transplant rejection occurs when the recipient's immune system recognizes the transplanted organ as foreign, leading to an attack by cytotoxic T cells.

Immunosuppressive drugs like calcineurin inhibitors and corticosteroids are used to suppress the immune response and prevent transplant rejection.

Specialized immune cells responsible for recognizing and destroying infected or abnormal cells.

Immune cells that orchestrate the immune response by activating other immune cells and promoting inflammation.

Immune cells that help maintain immune tolerance and prevent autoimmune reactions by suppressing the activity of other immune cells.

A type of T cell that persists after an infection is cleared and can mount a faster and stronger response upon re-exposure to the same antigen.

The process by which T cells are activated when they recognize antigens presented by MHC molecules on antigen-presenting cells.

A type of protein complex found on the surface of cells that plays a vital role in presenting antigens to T cells.

A molecule that triggers an immune response by binding to specific receptors on immune cells.

A type of immune cell that specializes in presenting antigens to T cells.

The specific region on an antibody that binds to an antigen's epitope.

A type of immunity that relies on B cells and antibodies circulating in the blood and lymph to neutralize pathogens.

When a B cell encounters its specific antigen, it binds to it via its B cell receptor (BCR) and receives signals from helper T cells. This activates the B cell to divide and differentiate into plasma cells and memory B cells.

These are the effector B cells that produce and release large amounts of antibodies specific to the encountered antigen.

These long-lived B cells remain in the body even after the initial infection has cleared. They provide a faster and stronger antibody response if the same antigen is encountered again.

A type of immunity that relies on T cells to directly attack infected cells or abnormal cells. It's crucial for defending against intracellular pathogens and cancer cells.

Antibodies can bind to soluble antigens, causing them to clump together and precipitate out of solution. This makes it easier for phagocytes to engulf them.

Antibodies can cause pathogens with antigens on their surfaces to clump together. This makes it easier for phagocytes to engulf them.

The spleen is a vital organ in the immune system that performs two crucial functions: filtering blood and fighting infections. Its red pulp filters out old or damaged red blood cells while the white pulp houses immune cells that combat pathogens.

Mucosa-associated lymphoid tissue (MALT) consists of immune cells and structures located in the mucous membranes of the digestive tract, respiratory system, and reproductive system. These areas are exposed to the external environment, so MALT helps protect them from infections.

Gut-associated lymphoid tissue (GALT) is a type of MALT found in the digestive tract. It plays a crucial role in preventing infections by preventing harmful bacteria and viruses from entering the bloodstream.

The adaptive immune system has the ability to remember past encounters with pathogens. This 'immunological memory' allows for a faster and more effective response during subsequent infections by the same pathogen.

MHC Class I molecules are found on all nucleated cells in the body. They present fragments of proteins from inside the cell (endogenous antigens) to CD8+ cytotoxic T cells. These T cells are like assassins that kill infected cells to prevent the spread of the pathogen.

MHC Class II molecules are found on antigen-presenting cells like macrophages, dendritic cells, and B cells. They present fragments of proteins from outside the cell (exogenous antigens) to CD4+ helper T cells. These T cells are like commanders that activate other immune cells to fight the infection.

An antigen is a substance that the immune system recognises as foreign. It can trigger an immune response to defend the body against foreign invaders like bacteria or viruses.

An epitope is a specific part of an antigen that an antibody or T cell receptor recognises and binds to. A single antigen can have many epitopes that can bind to different immune cells, allowing for a more targeted and effective immune response.