207 immunology terms

Activation

A process by which a cell changes or gains functions in response to a stimulus.

Adaptive immune cell

An immune cell involved in the adaptive immune response. includes B cells and T cells.

Adaptive immune response

One of the two main ways in which the immune system responds to pathogens. Provides long-lasting protection against specific pathogens but may take longer to start.

Antibody

A small protein that binds to a specific antigen. They are made by plasma cells and help the immune system fight pathogens in various ways. The human immune system can generate billions of types of these small proteins.

Antigen

A small piece of biological material (protein, carbohydrate, lipid, or nucleic acid) that can be recognized by the immune system. These pieces of biological material from pathogens or abnormal cells trigger an immune response.

Antigen-MHC complex

An antigen bound to an MHC protein on the surface of a cell. T cells must bind to a specific one in order to activate.

Antigen-presenting cell (APC)

A cell with an antigen bound to an MHC protein on its

surface. They interact with T cells to trigger an immune response. The most common ones are dendritic cells.

Apoptosis

A process by which a cell destroys itself. Involves several chemical reactions that make the cell change appearance and then die. It is often used to kill cells that are unneeded or abnormal.

Autoimmune disease

A condition in which the immune system mistakenly

attacks the body’s healthy, normal cells.

Basophil

An innate immune cell that circulates in the blood and is involved in inflammation.

B cell

An adaptive immune cell that helps target and destroy specific pathogens. After being activated by T cells, these cells differentiate into plasma cells to produce antibodies.

B cell receptor (BCR)

A protein on the surface of a B cell that binds to a specific antigen. Plays a major role in B cell activation.

Bone marrow

A spongy tissue in certain bones. Contains stem cells that develop into immune cells and red blood cells.

Cell-mediated immune response

The processes of the adaptive immune response that play a major role in destroying infected cells through cytotoxic T cells.

Complement proteins

A group of proteins in the blood that help destroy

pathogens and infected cells. They can damage

pathogens directly or attract other immune cells to the site of an infection.

Cytokines

Small proteins released by cells to communicate with

other cells. Some of these proteins alert immune cells to an

infection or activate certain immune cells.

Cytotoxic T cell

A type of T cell that kills infected cells by making them undergo apoptosis.

Dendritic cell

A type of phagocyte (innate immune cell that engulfs and destroys pathogens). They “display” antigens from the pathogens it engulfs in order to activate other immune cells.

Differentiation

A process that switches a cell from one type to another, typically more specialized type. It is caused by changes in gene expression that are often triggered by chemicals, including cytokines and hormones.

Engulf

surround and take in large particles (such as pathogens). The phagocyte extends its outer membrane around the particle, forming an enclosed structure called a vesicle that brings the particle into the cell.

Eosinophil

An innate immune cell that destroys large pathogens, such as parasites, by releasing damaging molecules and chemical signals (cytokines).

Helper T cell

A type of T cell that activates other immune cells, including B cells and cytotoxic T cells.

Histamine

A small molecule released by mast cells to trigger

inflammation. It makes blood vessels “leaky,” which allows immune cells and fluid to move from the blood vessels into body tissues.

Humoral immune response

The processes of the adaptive immune response that

involve antibodies (also known as the antibody-mediated response). These processes make and use antibodies to fight specific pathogens. They include B cell activation and differentiation into plasma cells, which produce antibodies.

Immune cells

Cells that are part of the immune system. Sometimes also called white blood cells or leukocytes.

Immune response

The processes that the immune system uses to fight

pathogens. Includes two main parts, the innate and

adaptive immune responses, and involves many cells and organs.

Immune system

A group of organs, tissues, cells, and molecules that

protect the body from pathogens.

Immunocompromised

A condition in which the immune system is “weakened” and less effective at fighting pathogens. A person could become this due to certain medications, medical conditions, viral infections, etc.

Inflammation

A process in the innate immune response that helps the body fight pathogens and repair tissue damage.

It is triggered by injury or infection and can result in redness, pain, and swelling.

Innate immune cell

An immune cell involved in the innate immune response. Includes phagocytes (macrophages, neutrophils, dendritic cells, etc.), mast cells, and natural killer (NK) cells.

Innate immune response

One of the two main ways in which the immune system responds to pathogens. Provides immediate protection but cannot target specific pathogens.

Lymph

A fluid similar to blood that circulates throughout the body. This fluid contains immune cells but not red blood cells.

Lymph nodes

Small organs throughout the body that contain many

immune cells. Lymphatic vessels connect through these small organs.

Lymphatic vessels

Thin “tubes” that carry a fluid called lymph throughout the body. These tubes are similar to blood vessels but do not contain red blood cells.

Lymphocyte

A type of immune cell. Includes T cells, B cells, and natural killer (NK) cells.

Lymphoid organs

A group of organs that produce or contain large numbers of immune cells. Examples include the bone marrow, thymus, lymph nodes, spleen, and tonsils.

Macrophage

An innate immune cell that plays many roles.

They are phagocytes that engulf and destroy pathogens and abnormal cells. They can also release chemical signals (cytokines) to attract other immune cells.

Major histocompatibility complex (MHC) protein

A protein that binds to antigens and “displays” them on the surface of a cell. Phagocytes use these proteins to “display” antigens from pathogens.

Mast cell

An innate immune cell that plays a major role in

inflammation. Releases chemical signals (histamine) that help fluid and immune cells move from the blood vessels into tissues.

Memory cells

Long-lived B and T cells that are made the first time a

pathogen infects the body. If the body is reinfected by the same type of pathogen, they provide a faster, stronger adaptive immune response.

Monocyte

An innate cell that differentiates into macrophages. Like macrophages, these are phagocytes that engulf and destroy pathogens and abnormal cells.

Mucous membrane

A thin tissue containing cells that make mucus. This lines the digestive system (gut), respiratory system (airways), and urogenital tract.

Mucus

A sticky, slimy substance produced by certain cells.

Protects tissues by trapping pathogens and contains

antimicrobial enzymes and antibodies.

Natural killer (NK) cell

An innate immune cell that kills infected and abnormal cells. Can release chemical signals (cytokines) that cause other cells to undergo apoptosis.

Neutralization

A process by which antibodies bind to a pathogen and block it from interacting with and infecting the body’s cells.

Neutrophil

An innate immune cell. Typically the first cell type to

respond to pathogens, particularly bacteria and fungi. Chemical signals (cytokines) can attract neutrophils and make them multiply.

Pathogen

A microbe that causes disease. Can include bacteria,

viruses, fungi, or parasites.

Phagocyte

An innate immune cell that engulfs and destroys

pathogens and abnormal cells. Includes neutrophils,

monocytes, macrophages, and dendritic cells.

Phagocytosis

A process by which immune cells called phagocytes engulf and destroy pathogens and abnormal cells. Parts of the destroyed pathogens or cells may be absorbed by the phagocyte, released, or displayed on the phagocyte’s MHC proteins.

Plasma cell

A type of adaptive immune cell that produces antibodies. Each cell makes an antibody for a specific antigen and makes several thousand copies of this antibody per second. They come from activated B cells.

Primary immune response

How the immune system responds the first time it

encounters a specific pathogen.

Progenitor cells

Cells that come from stem cells and can then differentiate into other cell types. Lymphoid cells differentiate into lymphocytes, and myeloid cells differentiate into other immune cells and red blood cells. Both types of cells come from stem cells in the bone marrow.

Receptors

Proteins in and on the membranes of cells. These bind to specific molecules, such as antigens, to send signals between or within cells.

Secondary immune response

How the immune system responds the second (or any

subsequent) time it encounters a specific pathogen. This response is faster and more powerful than the immune system response when it first encounters the pathogen.

Skin

The body’s thick outer layer. Acts as a physical barrier to pathogens and also makes some antimicrobial substances.

Stem cells

A cell that can develop into a variety of other cell types. These cells in the bone marrow can develop into immune cells and red blood cells.

T cell

An adaptive immune cell that helps the body respond to specific pathogens. Upon recognizing a specific antigen, T cells differentiate into helper T cells and cytotoxic T cells.

T cell receptor (TCR)

A protein on the surface of a T cell that binds to a specific antigen (but only when the antigen is bound to an MHC protein on an antigen-presenting cell). Plays a major role in T cell activation.

Thymus

An organ in the chest where immune cells called T cells develop.

Tonsils

Small organs at the back of the throat that contain

immune cells. These cells destroy inhaled or ingested

microbes and warn the immune system about potential infections.

Toxins

Harmful substances (typically small molecules or proteins) produced by living organisms, including some pathogens.

Vaccine

A substance that triggers an immune response against a pathogen without causing an infection. If the immune system encounters the same type of pathogen later, it can destroy the pathogen more quickly and efficiently than if the individual had not had one of these.