Unit 4 // AOS1 Textbook Definitions

Question 1

Pathogen

Answer 1

An agent that causes disease

Question 2

Antigen

Answer 2

Any molecule that may trigger an immune response

Question 3

Non-self antigen

Answer 3

A molecule from outside the body that is recognised by the immune system and initiates an immune response. Also know as foreign antigen

Question 4

Major histocompatibility complex (MHC) markers

Answer 4

A group of proteins present on the surface of all self-cells that enables the immune system to distinguish it from non-self material

Question 5

Major histocompatibility complex class I (MHC Class I) markers

Answer 5

Expressed on all nucleated cells in the body. These mark cells as ‘self’ so that the immune system doesn’t attack them

Question 6

Major histocompatibility complex class II (MHC Class II) markers

Answer 6

Expressed on antigen-presenting cells, which interact with T-helper cells in the process of antigen presentation

Question 7

Autoimmune disease

Answer 7

A disease in which an individual’s immune system initiates an immune response against their own cells

Question 8

Allergen

Answer 8

A non-pathogenic antigen that triggers an allergic reaction

Question 9

Allergic reaction

Answer 9

An overreaction of the immune system to a non-pathogenic antigen

Question 10

Cellular pathogen

Answer 10

A pathogen that has a cellular structure and exhibits the processes of a living organism. Examples include bacteria, fungi, protozoa and parasites

Question 11

Non-cellular pathogen

Answer 11

A pathogen that neither has a cellular structure no exhibits the processes of a living organism. Examples include viruses and prions

Question 12

Lysis

Answer 12

The disintegration or rupturing of a cell

Question 13

Hyphae

Answer 13

Branching filaments of a fungus which helps absorb nutrients from the environment

Question 14

Parasite

Answer 14

An organism that lives in or on another organism, usually deriving nutrition from the host organism

Question 15

Innate Immune System

Answer 15

A component of the immune system that is composed of generalised and non-specific defences and/or responses to pathogens. Also known as the non-specific immune system

Question 16

First line of defence

Answer 16

A component of the innate immune system characterised by the presence of physical, chemical, and microbiological barriers to keep pathogens out of the host organism

Question 17

Second line of defence

Answer 17

A component of the innate immune system characterised by the non-specific response to injury and/or pathogens by a variety of cells and molecules

Question 18

Non-specific

Answer 18

Describes a component of the immune system that responds the same way to all pathogens

Question 19

Physical barrier

Answer 19

A component of the first line of defence that features solid or fluid obstacles that block pathogen entry such as skin or mucus

Question 20

Chemical barrier

Answer 20

A component of the first line of defence that features the use of enzymes, toxins, and acids to protect against pathogen invasion

Question 21

Cuticle

Answer 21

A waxy protective film covering the surface of a plant leaf

Question 22

Gall

Answer 22

An abnormal outgrowth of tissue in plants designed to limit the spread of an invading pathogen

Question 23

Trichomes

Answer 23

Small hairs on the surface of plants used to deter pathogens and/or insects

Question 24

Microbiological barrier

Answer 24

A component of the first line of defence in which the presence of normal flora limits the growth of pathogenic bacteria.

Question 25

Cilium (pl. cilia)

Answer 25

Thin, hair-like projection that protrudes from eukaryotic cells

Question 26

Flora

Answer 26

Naturally occurring, non-pathogenic bacteria present in an organism

Question 27

Leukocytes

Answer 27

A group of blood cells responsible for protecting the body against pathogens and foreign materials. Also known as white blood cells

Question 28

Phagocytes

Answer 28

A group of leukocytes responsible for the endocytosis and destruction of pathogens, foreign material, and cell debris

Question 29

Neutrophil

Answer 29

The most common type of leukocyte in the body. Engages in phagocytosis of pathogens and foreign material, as well as the release of cytokines

Question 30

Macrophage

Answer 30

A type of leukocyte found throughout the body that engages in phagocytosis and antigen presentation

Question 31

Dendritic cell

Answer 31

A type of leukocyte that engages in phagocytosis and antigen presentation

Question 32

Antigen-presenting cell

Answer 32

A subgroup of phagocytes that display antigens from consumed pathogens on their surface and interact with the adaptive immune response

Question 33

Cytokine

Answer 33

A signalling molecule released by cells (typically in the immune system) which aids in communication between immune cells and helps protect against pathogens

Question 34

Natural killer (NK) cell

Answer 34

A type of leukocyte responsible for the recognition and destruction of damaged and/or infected host cells

Question 35

Mast cell

Answer 35

A type of leukocyte responsible for releasing histamine during allergic and inflammatory responses

Question 36

Degranulation

Answer 36

The release of granule contents from a cell

Question 37

Histamine

Answer 37

A molecule released by mast cells that plays a key role in inflammation

Question 38

Inflammatory response

Answer 38

A series of biochemical events that occur in the body as a result of infection and/or trauma. Characterised by swelling, redness, pain, and heat in the affected tissue.

Question 39

Eosinophil

Answer 39

A large granular leukocyte responsible for the release of toxic chemical mediators