Biology Chapter 7: Pathogens and the Immune System Vocabulary

A comprehensive set of vocabulary flashcards based on lecture notes covering pathogens, the three lines of defence, cellular components of the immune system, and the lymphatic system.

Pathogen

an agent that causes disease

Antigen

any molecule that may trigger an immune response

major histocompatibility complex (MHC) markers

a group of proteins present on the surface of all self-cells that enables the immune system to distinguish it from non-self material. Also known as MHC proteins, MHC molecules, or self-antigens

major histocompatibility complex class I (MHC Class I)

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

major histocompatibility complex class II (MHC Class II)

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

allergen

a non-pathogenic antigen that triggers an allergic reaction

allergic reaction

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

cellular pathogen

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

non-cellular pathogen

a pathogen that neither has a cellular structure nor exhibits the processes of a living organism. Examples include viruses and prions

lysis

the disintegration or rupturing of a cell

innate immune system

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.

first line of defence

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

second line of defence

a component of the innate immune system characterised by the nonspecific and immediate response to injury and pathogens by a variety of cells and molecules

non-specific

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

physical barrier

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

chemical barrier

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

microbiological barrier

a component of the first line of defence in which the presence of normal flora limits the growth of pathogenic bacteria. Also known as microbiota barrier

leukocytes

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

phagocyte

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

neutrophil

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

macrophage

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

dendritic cell

a type of leukocyte that engages in phagocytosis and antigen presentation

antigen-presenting cell

a subgroup of phagocytes that display antigens from consumed pathogens on their surface and interact with the adaptive immune system. Also known as professional antigen-presenting cell

cytokine

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

natural killer (NK) cell

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

mast cell

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

histamine

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

inflammatory response

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

interferon

a cytokine released by virally infected cells that increases the viral resistance of neighbouring uninfected cells

complement proteins

a number of different types of proteins found in the blood that opsonise, cause lysis, and attract phagocytes to invading pathogens

opsonisation

the mechanism by which complement proteins attach to the surface of pathogens, making them easier to phagocytose

vasodilation

the widening of blood vessels

third line of defence

a subset of the immune system within vertebrates that is composed of the humoral and cell-mediated responses which create a specific immune response and form immunological memory. Also known as the adaptive immune system or specific immune response

immunological memory

the ability of the immune system to quickly and aggressively combat a previously encountered pathogen due to the presence of T and B memory cells

T lymphocyte

a type of lymphocyte that plays an important role in cell-mediated immunity. It differentiates into cytotoxic T cells, T memory cells, and T helper cells

T helper cell (Th)

a type of differentiated T lymphocyte that supports the functioning of a number of different immune cells, including the cloning and differentiation of selected T and B cells

lymphatic system

a large network of vessels and tissues throughout the body that form an important component of both the circulatory and immune systems

lymph node

a small secondary lymphoid tissue of the lymphatic system where antigen-presenting cells activate the adaptive immune system

humoral immunity

an adaptive immune response in which extracellular pathogens are targeted by specific antibodies produced by plasma cells. Also known as B cell immunity

cell-mediated immunity

an adaptive immune response in which infected or abnormal cells are destroyed by cytotoxic T cells. Also known as T cell immunity

B lymphocyte

a type of lymphocyte that plays an important role in humoral immunity and differentiates into plasma cells and B memory cells

Antibody

a protein produced by plasma cells during the adaptive immune response that is specific to an antigen and combats pathogens in a variety of ways. Also known as immunoglobulin

clonal expansion

the process in which many copies of a lymphocyte are generated

clonal selection

the process in which B and T cells encounter an antigen that matches their antigen-binding site, and then generate many copies of themselves. Also known as clonal selection theory

differentiation

the process in which cells develop specialised characteristics, typically transforming them from one cell type to another more specialised cell type

B memory cell

a differentiated B lymphocyte that is responsible for providing long-lasting immunological memory of an antigen

effector cell

a cell that responds to a signal and produces a response

plasma cell

a differentiated B lymphocyte that is responsible for the generation and secretion of antibodies during the humoral response

lymph

a pale fluid that flows through the lymphatic system and has a high concentration of leukocytes

bone marrow

semi-solid tissue found within bones. Serves as the primary site of the creation of red blood cells and leukocytes

thymus

a primary lymphoid organ located in the chest. Serves as the site of T cell maturation