Chapter 8 Responding to Antigens (copy)

Allergen

an antigen that elicit an allergic response

Allergic response

the rapid and vigorous overreaction of the immune system to antigens called allergens. Involve the production of lgE by B lymphocytes and the release of histamine by mast cells

Antigen

A substance that react with antibodies and T lymphocyte receptors; those that induce an immune response are immunogens

Antigens presentation

The presentation of antigens by antigen-presenting cells

Antigen-presenting cell (APC)

A cell that uses MHC-II on its surface to present foreign antigens to helper T cells to elicit an adaptive immune reponse. Examples include dendritic cells and macrophages

Antigenic variation

The mechanism of changing surface antigens, usually to avoid detection or an immune attack. Employed by certain protozoans such as *Plasmodium* spp.

Basophil

A type of white blood cell (leukocyte) that releases histamine during an allergic reaction

Cellular pathogen

A cellular organism that is a source of non-self antigens and causes disease in a host organism. Bacteria, protozoa, oomycetes, fungi, several types of worms and arthropods are all types

Chemical barrier

A chemical product or mechanism that is one of the first-line defences of an organism’s immune system. Examples include the lysozyme enzymes in saliva

Chemokine

A cytokine that attracts white blood cells to the site of infection

Complement protein

A protein that is able to kill foreign cells by lysis. There are more than 30 different types that are activated in response to antigen-antibody complexes, antigens and carbohydrates on the surfaces of some bacteria and parasites

Cytokine

One of a group of peptides and proteins released from cells that are important in cell signalling, particularly between cells of the immune system

Defensin

Molecule that is active against bacteria, fungi and certain viruses

Dendritic cell

A type of antigen-presenting cell

Eosinophil

A type of leukocyte that predominates in parasitic infections and contains granules that are stained by dye

Extracellular pathogen

A pathogen that does not invade calls but lives and reproduces in the extracellular environment

Fever

An increase in body temperature that results from the regulated body temperature set point in the hypothalamus of the brain being set to a higher level by inflammatory cytokines, to slow the replication of bacteria and improve the adaptive immune response

Granulocyte

A type of white blood cell containing granules (sacs filled with enzymes that digest pathogenic microorganisms). Neutrophils, basophils are examples.

Histamine

An organic compound involved in inflammatory responses and allergic reactions, which causes surface blood vessels to dilate and become more permeable to immune cells and fluids. Common hay fever symptoms such as runny nose and eyes and sneezing are the results of histamine action and aimed at flushing out allergens

Inflammation

A protective response, triggered by damaged tissue or invading pathogens, that leads to increased blood flow and migration of white blood cells to the site of damage/infection. It results in heat, pain, swelling, redness and loss of function

Innate immune response

Non-specifically and rapidly protects against a wide variety of pathogens using innate immune cells such as leukocytes (e.g. phagocytes) and defensive molecules such as complement proteins. Is triggered when the physical, chemical and microbiological barriers that provide resistance to infection are breached

Innate immunity

Non-specifically protects against a wide variety of pathogens. It consists of physical, chemical and microbiological barriers that provide resistance to infection, and an innate response to infection that involves leukocytes such as phagocytes and defensive molecules such as complement proteins

Interferon

A type of cytokine important in antiviral immunity. Are produced by virus-infected cells to inhibit viral replication by resulting in the transcription of antiviral genes and the expression of antiviral proteins; they have a lesser role in bacterial and parasitic immune responses. They regulate the immune response in a number of ways, such as enhancing T lymphocyte activity

Intracellular pathogen

A pathogen that invades cells and requires a host cell to survive and/or reproduce

Leukocyte

A white blood cell; includes phagocytes and lymphocytes

Lysis

The destruction of a cell, usually by rupturing the plasma membrane

Lysozyme

An antibacterial enzyme present in body secretions such as saliva and tears. It disrupts the bacterial cell wall

Macrophage

A type of large white blood cell that is responsible for engulfing and digesting foreign matter in the body, as well as damaged cells or the remnants of apoptosis

Major histocompatibility complex (MHC)

A complex of genes that code for proteins on the surface of cells that are involved in antigen presentation to T lymphocytes

Mast cell

An immune cell containing granules of histamine. This cell mediates allergic responses by binding lgE allergen complexes and releasing histamines

Microbiological barrier

A microbial agent that is one of the first line defences of an organism’s innate immune system, such as the non-pathogenic bacteria (microbiota) found on the skin and in part of the digestive and excretory systems

Microbiota

Microorganisms that colonise particular sites; normally do not cause disease

Microflora

Bacteria and microscopic fungi and algae that colonise a particular site. Are a set of microbiota.

Natural killer cell (NK cell)

A type of lymphocyte that is involved in the innate immune response. Recognise and destroy tumour and virus-infected cells

Neutrophil

A type of leukocyte for which phagocytosis is a major role. Also release defensins to destroy pathogens and cytokines to recruit and activate other leukocytes in response to infection. Are the most common leukocyte in mammals, accounting for 60-70% of all white blood cells

Non-cellular pathogen

A non-cellular, non-living agent that causes disease. Include viruses, viroids and prions,

Non-self antigen

An antigen that does not belong to an organism’s own cells

Pathogen/Infectious agent

An organism that can produce disease in another organism; includes many microorganisms and parasites

Phagocyte

A cell capable of engulfing pathogens or foreign particles to destroy them

Phagocytosis

The engulfment of solid materials in which the plasma membrane surrounds the material, forming a vacuole (phagosome) and allowing the substance into the cell

Physical barrier

A physical entity that is one of the first-line defences of an organism’s immune system. Such as skin or bark

Prion

A small protein particle that, when its shape is altered due to mutation, causes protein aggregation and is toxic to neurons. Are the cause of the spongiform encephalopathy diseases BSE in cattle and CJD in humans

Self-antigen

An organism’s own antigen, which is normally tolerated (does not elicit an immune response)

Self-tolerence

The inability of the adaptive immune system to respond to self-antigen

Viroid

An infectious agent of plants that is a type of self-cleaving RNA enzyme (or ribozyme); composed of short, circular strands of RNA that lack a protein coat

Virus

An infectious agent composed of genetic material (DNA or RNA) enclosed in a protein coat, and sometimes also a lipoprotein envelope; is only able to multiply in a host cell