Chapter 7 - Dealing with disease Flashcards
afferent lymphatic vessel
thin-walled structures that collect lymph from the tissues of the body and deliver it to lymph nodes
agglutination
the clumping of particles together. In the immune system, antibodies can help clump pathogens together
allergen
a non-pathogenic antigen that triggers an allergic reaction
allergic reaction
an overreaction of the immune system to a non-pathogenic antigen
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
antigen-antibody complex
a structure formed by the complementary binding between antigen and antibody molecules
antigen-presenting cell
a subgroup of phagocytes that display the antigens from consumed pathogens on their surface and interact with the adaptive immune system
antigen
any molecule that may trigger an immune response
apoptosis
the controlled death of cells in the body. Also known as programmed cell death
autoimmune disease
a disease in which an individual’s immune system initiates an immune response against their own cells
B lymphocyte
a type of lymphocyte that plays an important role in humoral immunity and differentiates into plasma cells and B memory cells
B memory cell
a differentiated B lymphocyte that is responsible for providing long-lasting immunological memory of an antigen
bone marrow
semi-solid tissue found within bones. Serves as the primary site of the creation of red blood cells and leukocytes
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
cellular pathogen
a pathogen that has a cellular structure and exhibits the processes of a living organism. Examples include bacteria, fungi, protozoa, and parasites
chemical barrier
a component of the first line of defence that features the use of enzymes, toxins, and acids to protect against pathogen invasion
chemotaxis
the attraction of phagocytes towards a pathogen
cilium (pl. cilia)
thin, hair-like projection that protrudes from eukaryotic cells
circulatory system
a collection of tissues and organs involved in the transportation of substances around the body. Composed of the lymphatic and cardiovascular systems
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
complement cascade
a complex sequence of events which occurs after the activation of complement proteins
complement proteins
a number of different types of proteins found in the blood that opsonise, cause lysis, and attract phagocytes to invading pathogens
cuticle
a waxy protective film covering the surface of a plant leaf
cytokine
a signalling molecule released by cells (typically in the immune system) which aids in communication between immune cells and helps protect against pathogens
cytotoxic T cell (Tc)
a differentiated T lymphocyte that is responsible for the destruction of infected or abnormal cells
degranulation
the release of granule contents from a cell
dendritic cell
a type of leukocyte that engages in phagocytosis and antigen presentation
differentiation
the process in which cells develop specialised characteristics, typically transforming them from one cell type to another more specialised cell type
disulphide bond
a strong covalent bond occurring between two sulphur atoms
effector cell
a cell that responds to a signal and produces a response
efferent lymphatic vessels
thin-walled structures that collect lymph that has drained through lymph nodes, returning it back to circulation
eosinophil
a large granular leukocyte responsible for the release of toxic chemical mediators
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
flora
naturally occurring, non-pathogenic bacteria present in an organism
gall
an abnormal outgrowth of tissue in plants designed to limit the spread of an invading pathogen
histamine
a molecule released by mast cells that plays a key role in inflammation
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
hyphae
branching filaments of a fungus which help absorb nutrients from the environment
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
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
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.
interferon
a cytokine released by virally infected cells that increases the viral resistance of neighbouring uninfected cells
leukocytes
a group of blood cells responsible for protecting the body against pathogens and foreign material. Also known as white blood cells
lymph
a pale fluid that flows through the lymphatic system and has a high concentration of leukocytes
lymph node
a small secondary lymphoid tissue of the lymphatic system where antigen-presenting cells activate the adaptive immune system
lymphatic capillaries
the smallest form of lymphatic vessel. Located in the spaces between 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
lysis
the disintegration or rupturing of a cell
macrophage
a type of leukocyte found throughout the body that engages in phagocytosis and antigen presentation
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
mast cell
a type of leukocyte responsible for releasing histamine during allergic and inflammatory responses
membrane attack complex (MAC)
a pore formed by complement proteins in the cell membranes of a pathogen, disrupting the membrane and leading to the pathogen’s destruction
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
natural killer (NK) cell
a type of leukocyte responsible for the recognition and destruction of damaged and/or infected host cells
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
non-cellular pathogen
a pathogen that neither has a cellular structure nor exhibits the processes of a living organism. Examples include viruses and prions
non-self antigen
a molecule from outside the body that is recognised by the immune system and initiates an immune response. Also known as a foreign antigen
non-specific
describes a component of the immune system that responds the same way to all pathogens
opsonisation
the mechanism by which complement proteins attach to the surface of pathogens, making them easier to phagocytose
parasite
an organism that lives in or on another organism, usually deriving nutrition from the host organism
pathogen
an agent that causes disease
phagocyte
a group of leukocytes responsible for the endocytosis and destruction of pathogens, foreign material, and cell debris
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
plasma cell
a differentiated B lymphocyte that is responsible for the generation and secretion of antibodies during the humoral response
primary lymphoid tissue
components of the lymphatic system that are responsible for the production and maturation of lymphocytes. Includes bone marrow and the thymus
Rhesus antigen
an antigen on the surface of red blood cells that can cause an immune response if not matched correctly between donor and receiver
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
second line of defence
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
secondary lymphoid tissue
components of the lymphatic system that are responsible for the maintenance of mature lymphocytes and the activation of the adaptive immune response. Includes lymph nodes and the spleen
spleen
an organ located in the upper abdomen that serves a variety of functions in the immune
system and the regulation of red blood cells
stoma (pl. stomata)
a small pore on the leaf’s surface that opens and closes to regulate gas exchange
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
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 memory cell
a differentiated T lymphocyte that is responsible for providing long-lasting immunological memory
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
thymus
a primary lymphoid organ located in the chest. Serves as the site of T cell maturation
tonsils
the name given to the two lymph nodes that reside at the back of the throat
trichomes
small hairs on the surface of plants used to deter pathogens and/or insects
vasodilation
the widening of blood vessels
Steps in the inflammatory response:
INITIATION - In response to injury, macrophages situated in the tissue become activated and, along with damaged cells, release cytokines. Additionally, mast cells degranulate, releasing histamine.
VASODILATION - The histamine released from mast cells travels to nearby blood vessels and binds to specific receptors, causing vasodilation. This causes blood vessels to widen, increasing blood flow to the injury site, and this is the reason behind the swelling, redness, and warmth we often associate with inflammation. Additionally, the formation of gaps in the vessel wall increases its permeability to cells of the immune system.
MIGRATION - Vasodilation and the increased leakiness of blood vessels allow for a number of innate immune system components to leave the bloodstream and enter the site of injury. These components include:
* Phagocytes, including macrophages and neutrophils, are guided by the cytokines secreted by activated macrophages and damaged cells to the site of injury. Here, they phagocytose pathogens and digest them using enzymes such as lysozymes.
* Complement proteins are attracted to pathogens and make it easier for phagocytes to destroy them.
Steps in humoral immune response:
1) A pathogen w antigen complementary to antigen-binding site on receptor of a B cell interacts with that B cell. -> the B cell is ‘selected’.
2) T helper cell selected through antigen presentation (also has a complementary receptor to antigen) recognises the selected
B cell -> secretes different cytokines. -> cause the B cell
to undergo clonal expansion, (many copies of the selected B cell are produced.) (clonal selection theory.)
3) cytokines also stimulate the selected B cell to undergo the process of differentiation (selected B cell driven to differentiate into two different types of B cells –> B memory cells and effector cells (plasma cells.))
4) Plasma cells = differentiated clones of the selected B cell. After differentiating, they
secrete antibodies into the blood in order to defend against the selected pathogen.
B memory cells = clones of the selected B cell that reside in the body for a prolonged period of time and are responsible for immunological memory
Key functions of antibodies:
Neutralisation - Antibodies can block the sites of pathogens that are used to attack host cells (e.g. the site used by a virus to enter a cell) and can block the active sites of toxins.
Agglutination - Antibodies can bind together with antigens on two separate pathogens, forming large antigen-antibody complexes. This makes it easier for phagocytes to recognise the pathogens as foreign bodies and destroy them.
Immobilisation - Antibodies can also restrict the movement of pathogens around the body through the formation of large antigen-antibody complexes.
Opsonisation - Antibodies can bind directly to the surface of a pathogen to make it easier to phagocytose.
Activation of complement proteins - Antibodies attached to the surface of pathogens can
facilitate the actions of complement proteins, including the formation of membrane attack complexes (MACs).
Steps of cell mediated immune response:
1) At the same time as the selection of T helper cells, antigen-presenting cells eventually come upon a naïve T cell with a T cell receptor that matches the antigen being presented, initiating clonal selection -> naïve T cell
becomes selected -> stimulated by cytokines released by the selected T helper cell to undergo the processes of clonal expansion and differentiation
2) The clones of the selected T cell differentiate into two types of T cells – effector cells called cytotoxic T cells, and T memory cells. T memory cells, like B memory cells, are copies of the originally selected T cell that reside in the body for extended periods of time and help form immunological memory. The majority of selected T cells differentiate into cytotoxic T cells, which leave the lymph node and travel throughout the body, eventually reaching the site of infection.
