Unit 4 AOS 1 Flashcards
What are antigens
molecules or parts of a molecule that stimulate immune response through the adaptive immune response.
antibodies definition
proteins produced by plasma cells in response to antigens and which react specifically with the antigen that induced their formation
immunoglobulins definition
antigen-binding proteins produced by B cells and released in blood and lymph
inflammation definition
an innate reaction by the immune response to foreign particles or injury resulting in redness and swelling
Cytotoxic T cell definition
T cells that are activated by cytokines to bind to antigen–MHC-I complexes on infected host cells and kill infected body cells
what are the 2 ways antigens can be classified as
self or non-self
self antigens are:
those that are not foreign and are thus usually tolerated by the immune system
non-self antigens definition
Non-self antigens can be identified as invaders and can be attacked by the immune system.
what is the main way for an immune cell to tell self and non-self antigens apart
the cell surface receptors that tell them if they are self or non-self (MHC)
what is the major histocompatibility complex
receptor proteins on the surface of cells that identify the cells as ‘self’
where are MHC-l markers found
all nucleated cells
what do MHC-l markers do
provide a site for binding of antigens to occur, that allows cells to be recognised as ‘self’ so they will not be attacked
Where are MHC-ll markers found
- mainly on specific white blood cells, including antigen-presenting cells (macrophages and dendritic cells)
- and helper T cells.
what do MHC-ll markers do
the antigen presenting cells present antigens on their surface on these MHC-II markers, which bind to helper T cells to help activate the adaptive immune response.
what is a pathogen
A pathogen or infectious agent is a biological agent that causes disease or illness to its host
what are the 2 types of pathogens
- cellular
- and non-cellular
how do cellular and non-cellular pathogens reproduce
- cellular reproduce independently
- non-cellular hijack the host’s processes in order to replicate.
what are the 4 main cellular pathogens
- bacteria
- parasites
- fungi
- protozoa
cellular pathogens definition
any disease-causing agent made up of cells that can reproduce independently without relying on the host machinery
what are cellular pathogens also referred to as
microorganisms (microbes)
what type of cell are cellular pathogens
can be both eukaryotes or prokaryotes
are bacteria prokaryotic or eukaryotic
prokaryotic
is bacteria intracellular or extracellular
they can be both
what is a major reason why bacteria is a pathogen (what do they produce)
toxins
what do bacteria toxins do
damage particular tissues of their host organism and cause disease
what are the 2 types of bacterial toxins
endotoxins and exotoxins
exotoxins definition
toxins that are secreted into the surrounding medium by a microorganism as it grows
endotoxins definition
toxic parts of the outer membrane of some Gram-negative bacteria that are released when the bacteria die
are protozoans prokaryotic or eukaryotic
eukaryotic, single celled
are fungi prokaryotic or eukaryotic
eukaryotic
what does it mean when said fungi are opportunistic pathogens
when it has the chance, bacteria can become a pathogen externally or internally
what are 3 examples of paracites
- roundworms
- hookworms
- and whipworms
are fungi prokaryotic or eukaryotic
eukaryotic
main difference between eukaryotic and prokaryotic cells
eukaryotic cells have a distinct nucleus containing the cell’s genetic material, while prokaryotic cells don’t have a nucleus and have free-floating genetic material instead
what are the 2 main non-cellular pathogens
- viruses
- prions
- and viroids (littler one)
virus definition
non-cellular pathogens that use the host cell in order to replicate their genetic material
prions definition
infectious particles made of protein that lack nucleic acids (folded proteins)
viroids definition
simple forms of viruses that lack a capsid
how can viruses travel to other organisms
Virions are the means by which a virus can transfer from one host cell to another
what do all viruses have (structure)
- genetic material, either DNA or RNA, organised as a single molecule or as several molecules
- a protein shell, known as a capsid, that surrounds the genetic material.
what is the protein shell and genetic material called together
nucleocapsid
how do viruses spread (release particles from cell)
The mode of release of viral particles from an infected cell may be by budding or by cell lysis.
what is lysis
destruction of cells by rupturing the membrane of the cell
what do prions do
triggers normal proteins in the brain to fold into an abnormal structure
what 2 forms can a prion be in
- a normal harmless cellular form of the protein, denoted PrPC
- a harmful infectious prion form of the protein, denoted PrPSc.
what is an incubation period
the time period between infection and the first appearance of the symptoms of a disease
what pathogen has a long incubation period
prions
do prions produce and immune response
no
what is an allergen
an antigen that elicits an allergic response
what systems do allergic response involve
cells from both the innate and adaptive system
what are the two major subdivisions of immunity
- innate immunity
- adaptive immunity
immunity definition
resistance to infectious disease
innate immunity definition
the type of immunity that is present from birth, is fast acting but not long lasting, and produces non-specific (generic) responses against classes of pathogens
adaptive immunity definition
an immune response that is specific to a particular antigen and develops through contact with an antigen
immunological memory definition
ability of the adaptive immune response to remember antigens after primary exposure
what are the 2 types of actions that the immune system uses to protect against infection
- cell-mediated immunity
- humoral immunity
cell-mediated immunity definition
immune response that is mediated by immune cells
humoral immunity definition
immune response mediated by soluble molecules in the blood, lymph and interstitial fluid that disable pathogens
what kinds of cells are all cells in the immune system
white blood cells
where do the white blood cells of the immune system derive from
they are derived from multipotent stem cells in the bone marrow
lymphocytes definition
class of white blood cells found in all tissues including blood, lymph nodes and spleen, and which play a role in specific immunity
B cells (B lymphocytes) definition
white blood cells that recognise antigens or pathogens and produce a large number of antibodies specific to an antigen
T cells (T lymphocytes) definition
white blood cells that mature in the thymus and participate in the adaptive immune response
what happens in the lymph nodes
B cells and T cells are activated and adaptive immune responses occur
what is apart of the 1st line of defense
physical, chemical and microbiological barriers to prevent pathogens from gaining entry to the body
what is apart of the 2nd line of defense
the actions of immune cells and soluble proteins mounting a rapid but non-specific attack against pathogens that gain entry to the body.
what is apart of the 3rd line of defense
the recognition of specific antigens by lymphocytes
what type of immunity do the 1st and 2nd line of defense use
innate immunity
what type of immunity does the 3rd line of defense use
adaptive immunity
What are the 3 barriers that prevent the entry of pathogens into an organism (1st line)
- physical barriers
- chemical barriers
- microbiological (microbiota) barriers
physical barriers definition
innate barriers that act to prevent the entry of pathogens into the body
chemical barriers definition
innate barriers that use enzymes to kill pathogens and prevent invasion into a host
microbiological barriers definition
innate barriers involving normal flora in the body
in vertebrates what is a physical barrier
epithelial tissue (intact skin, mucous membrane)
what is 2 examples of chemical barriers
sweat and tears
how to chemical barriers (sweat and tears) kill pathogens
by an enzyme called lysozyme that kills the pathogens
what is normal flora (microbiota barrier)
non-pathogenic bacteria that are the normal residents in particular regions of the body
how do microbiota barriers stop pathogens
they inhibit the growth of pathogenic microbes
what are 2 examples of plants physical barriers and how they stop pathogens
- cuticle (a waxy covering on leaves that reduces water accumulation and helps prevent cells becoming infected)
- stomata (can be closed to prevent pathogens entering)
what are 2 chemical barriers produced by plants and how do they work
- Caffeine (Toxic to fungi and insects)
- Saponin (Plant proteins that disrupt bacterial and fungal cell membranes)
when does the second and third line of defense start to work
when pathogens have entered the body (cut in skin)
phagocytosis definition
bulk movement of solid material into cells where the cell engulfs a particle to form a phagosome
what are the 3 key aspects of innate immunity
- soluble proteins
- inflammation
- immune cells
what are the 6 main white blood cells (immune cells)
- natural killer cells (NK cells),
- mast cells,
- eosinophils
- macrophages
- neutrophils
- dendritic cells
what are two other names for immune cells
- white blood cells
- leukocytes
which of the 6 immune cells are phagocytes
- neutrophils
- dendritic cells
- macrophages
where are neutrophils, eosinophils and NK cells found
in the bloodstream
where are the phagocytic cells found
in the tissues
what are the 2 granulocytes
eosinophils, neutrophils
what are granulocytes
a type of white blood cell that has small granules inside their cytoplasm
which immune cells are antigen presenting
- dendritic cells
- Macrophages
simple overview of steps in phagocytosis
- pathogen recognised by pattern recognition receptor
- pathogen engulfed by phagosome
- Lysosomes fuse with the phagosome
- pathogen is destroyed by toxic chemicals and lysosome
- material is discharged by exocytosis
In these antigen presenting cells what is on their surface (specifically MHC-ll markers) once phagocytosis happens
some antigens or sub-units from the digested pathogen on the MHC-ll markers (activating adaptive immune system)
macrophage info (brief)
they identify eliminate and engulf pathogens by phagocytosis and clear dead cells and debris. Also antigen presenting (can activate adaptive immune response)
Neutrophils info (brief)
Neutrophils are abundant immune cells that are usually the first to the site of an infection, engulfing and destroying pathogens.
dendritic cells info (brief)
Dendritic cells are professional antigen-presenting cells, engulfing pathogens and presenting their antigens to T cells to activate the adaptive immune response.
eosinophils info (brief)
assist in defending against larger parasitic agents that are too large to be engulfed by phagocytosis. They contain granules with toxic chemicals and histamine
NK cells info (brief)
lymphocytes that kill virus-infected cells through apoptosis, destroying both the cell and any viruses it contains. This prevents the virus infecting other cells.
degranulation info for NK cells
There granules contain granzymes and perforin. The perforin makes holes in the cells plasma membrane allowing the granzymes to enter. This enzymes induces apoptosis
degranulation definition
the process by which immune cells release various chemicals (such as histamine and antimicrobials) stored within secretory vesicles known as granules
mast cells info (brief)
they are vital in the inflammatory response. As well as releasing histamines that increase vascular permeability, they also release cytokines that attract other immune cells to help destroy the pathogen. (out of granules) (also contain heparin)
histamine definition
a substance involved in inflammation and allergic reactions that causes blood vessels to dilate and become more permeable to immune cells
what is the cell-mediated immunity for the second line of defense
the immune cells attacking the pathogen
what is the humoral immunity for the second line of defense
complement proteins and cytokines.
what are complement proteins
proteins that assist other innate immune cells and can destroy bacterial cells by lysis
what are cytokines
signalling molecules of the immune system
what is an important cytokine in the innate immune system and definition
interferons,
proteins secreted by some cells, in response to a virus infection, that helps uninfected cells resist infection by that virus
where are complement proteins found
dissolved in blood plasma
what are the 3 things that complement proteins do
- opsonising pathogens
- recruiting immune cells involved in an inflammatory response (chemotaxis)
- destroying bacterial pathogens by lysis
opsonisation definition
the coating of the surface of pathogen cells by complement proteins, making the pathogens more susceptible to phagocytosis
Why does opsonisation make pathogens more susceptible to phagocytosis
phagocytes have receptors for complement proteins on their plasma membranes, and these bind to the opsonised microbes. Allowing for direct binding to the pathogen
what is chemotaxis
movement of a cell or organism in response to a chemical substance
how does chemotaxis work for complement proteins
Small complement peptides that diffuse from the pathogen surface act as chemical signals, attracting immune cells involved in the inflammatory response
what is the membrane attack complex (MAC)
one of the defence mechanisms resulting from activation of complement proteins that destroys pathogen cells by osmotic shock
how does lysis work with complement proteins
complement proteins interact with pathogens allowing for the MAC to form on there plasma membrane. Lysis then occurs
how does lysis work
The MAC inserts into the plasma membrane of the pathogen and produces a pore that allows fluid to enter, causing the pathogen cell to swell and burst — explosive death by osmotic shock
are complement proteins inactive enzymes?
yes
how are complement proteins activated (cascade attached)
The activation of a complement protein occurs when the protein is cut (cleaved) into two fragments — a larger activated protein and a smaller peptide fragment. This sequence of reactions starts a cascade that can neither be stopped nor reversed.
Or C3 makes direct contact with molecules on the surface of a pathogen
process involved in complement activation (2 steps)
- The activation of an initial complement protein (known as C3) starts a sequence of reactions that take place on the surface of a pathogen. The first protein in the series enzymatically alters the next protein in the series.
- The product of the first reaction then activates the next enzyme in the series, which, in turn, activates the next protein, and so on.
how do infereons work
Once a body cell is infected with viruses, the cell secretes interferons. That cell is doomed, but the interferons that it secretes into its surroundings act as warning signals to nearby cells so that they can prepare in advance for a possible virus infection.
what are the roles of infereons (4)
- induce transcription of a number of specific genes that encode production of inactive forms of antiviral enzymes, inhibiting protein synthesis and destroying RNA. (only if virus succeeds in infecting the cell)
- make the plasma membrane less fluid (fusion with viral particles more difficult, so cant infect)
- cause virus-infected cells to undergo apoptosis
- activate immune cells,
what are the 5 main symptoms of inflammation
- redness
- pain
- heat
- swelling
- pus
what causes the redness in inflammation
due to vasodilation of blood vessels, leading to red blood cells released into tissue
what causes the pain in inflammation
due to the systemic response (such as fever), the stimulation of nerve endings through the release of bradykinin and histamine, and swelling putting pressure on pain receptors
what causes the heat in inflammation
due to increased blood flow
what causes the swelling in inflammation
due to the movement of fluid into tissues after vasodilation
what causes the pus in inflammation
due to dead phagocytes and cell debris.
what are the 3 stages of inflammation
- the vascular stage, (blood vessels)
- the cellular stage, (immune cells)
- the resolution stage, (stopped and restored)
what happens in the vascular stage of inflammation
The damaged cells release cytokines (attract neutrophils), and the mast cells release histamines (dilates blood vessels)
The blood vessels dilate (vasodilation) allowing for more immune cells to get into the infected area
what happens in the cellular stage of inflammation (brief)
The cellular stage involves further intervention from immune cells, particularly phagocytic cells.
what happens in the resolution stage of inflammation (brief)
Resolution involves the release of many active molecules or mediators, including anti-inflammatory cytokines.
what are the 4 functions of the lymphatic system
- production and maturation of immune cells
- the removal of excess fluids from body tissues
- absorption and transportation of fatty acids to the digestive system
- allowing for the process of antigen recognition by T and B lymphocytes.
what 4 things does the lymphatic system have in it (structure)
- lymph
- lymphatic vessels
- primary lymphoid organs
- secondary lymphoid organs
what are the primary lymphoid organs
bone marrow and thymus
what are the secondary lymphoid organs
lymph nodes and spleen
what is lymph
is the fluid in the lymphatic system that gets squeezed out of blood vessels
what happens in the bone marrow
- source of pluripotent stem cells (where immune cells originate)
- and site of maturation of B cells
what happens in the thymus
site where T cells mature after being released from the bone marrow
what happens in the spleen
- filters the blood passing through it, clearing the blood of bacteria and viruses as well as worn-out red blood cells
- contains T cells and B cells that detect and respond to infectious agents in the blood
- contains other immune cells
what are lymph nodes
Lymph nodes are the sites in which antigen recognition occurs
what is antigen recognition
This is where antigen-presenting cells display their antigens to their specific T and B lymphocytes, leading to expansion of the appropriate lymphocytes for adaptive immunity
7 steps involved with antigen presenting and initiation of immune response (adaptive immune response)
- The pathogen is engulfed into a phagosome, which fuses with a lysosome
- Digested by enzymes in the lysosome.
- Some of the fragments (digested parts of an antigen) are released by exocytosis.
- Some digested fragments of antigen are displayed on the MHC-II receptors on the surface the APC
- These APC’s move to the lymph node and present them to naïve helper T cells that carry specific receptors for that antigen. (antigen presentation)
- helper T cells undergo expansion, and clones are produced.
- Helper T cells assist other immune cells by releasing specific cytokines (named interleukins).
what do the helper T cells cytokines do to other cells
These can initiate either the humoral adaptive immune system (through stimulating the clonal selection and clonal expansion of B cells) or the cell-mediated immune system (through stimulating the clonal selection and expansion of cytotoxic T cells).
what is the function of helper T cells
- activate cytotoxic T cells
- activate B cells into becoming antibody-producing plasma cells
- activate macrophages to remove antibody-coated pathogens by phagocytosis
what is the two main features of the adaptive immune response
- specificity
- Immunological memory
what is specificity (adaptive response)
the ability to recognise and respond to specific antigens
3 key components of adaptive immune response
- T cells and B cells
- antibodies, also known as immunoglobulins
- lymph nodes, organs where B cells and T cells meet foreign antigens and are activated
what is the humoral immune response for the adaptive response
Involves the actions of antibodies that identify and bind to extracellular pathogens, to toxins and to other extracellular foreign antigens. Antibodies are products of special B plasma cells.
what is the cell-mediated immune response for the adaptive response
involves various actions of T cells. Cytotoxic T cells eliminate body cells that are infected by pathogens or have abnormal or missing self markers. They eliminate intracellular pathogens.
where do T cells develop
thymus
where do B cells develop
bone marrow
what are naive B and T cells
B and T cells that havent been activated
what are the 2 types of B cells
- B plasma cells
- B memory cells
what are the 5 steps of activation of humoral response
- new antigen reaches lymph nodes (APCs) and a specific B cell that matches will bind to the antigen on the APC
- Helper T cell release cytokines to activate correct T cells
- the plasma B cells and memory B cells are made (differentiation of naive B cell)
- plasma B cells secrete antibodies to the antigen
- Memory B cells remain in the lymphoid tissue
what is in clonal selection
when the correct naive B or T cell binds to the antigen
what is in clonal expansion
when the naive B or T cell differentiates
what are the 2 regions of an antibody
- variable region (ends that bind to antigens)
- constant region (most of the antibody)
what are the chains of an antibody
light and heavy chains (light short, heavy long)
another name for variable region (antibody)
antigen-binding sites
what is acronym to remember what antibodies can do to pathogens and what does it stand for
PIANO, Precipitation, Inflammation, Agglutination, Neutralisation and Opsonisation
what is precipitation (antibodies)
bind to soluble antigens, making them insoluble, causing them to precipitate out of the solution, creating a solid (more visible)
inflammation (antibodies)
release histamine, triggering inflammation
what is agglutination (antibodies)
bind to the surface antigens on pathogens to form antigen–antibody complexes, causing them to clump together (more visible)
what is neutralisation (antibodies)
bind to surface antigens on pathogens and form a coating that neutralises pathogens by blocking their receptors so that the pathogens cannot attach to healthy body cells and infect them
what is opsonisation (antibodies)
bind to the surface antigens on pathogens to form antigen–antibody complexes and tag the pathogen for destruction. This activates phagocytes and complement proteins
cell-mediated adaptive response definition
a specific response in which cytotoxic T cells destroy virus-infected cells using perforin and granzyme B
what types of pathogens do cytotoxic T cells destroy
intracellular pathogens
how do cytotoxic T cells recognise and bind to infected cells
the MHC-I marker
what happens in the 6 steps of activating the cell-mediated adaptive response
- APC displaying foreign antigens on their MHC-II markers bind to their specific helper T cells
- Helper T cells undergo clonal selection and expansion, (effector helper T cells and memory T cells)
- Interleukins are secreted by the helper T cell to stimulate immature T cells.
- Immature cytotoxic T cells also bind to the self-cell with abnormal foreign MHC-I markers or APC displaying foreign antigens
- cytotoxic T cells proliferate, producing activated cytotoxic T cells and memory T cells through clonal selection and expansion
- cytotoxic T cells destroy the cell via apoptosis
how do cytotoxic T cells do apoptosis
- release perforin, making a hole in the cell
- secrete granules (granzyme B) enter the cell and initiate apoptosis
what are the two ways we can gain immunity depending on the source of the antibody
- actively (active immunity)
- passively (passive immunity)
what is active immunity
the production of antibodies by a person in response to exposure to a particular antigen
what is passive immunity
short-term immunity acquired from an external source of antibodies
what are the two means of gaining immunity
- natural immunity
- artificial immunity
what is natural immunity
a form of specific immunity in which antibodies are produced or obtained through natural means
what is artificial immunity
immunity that is formed through deliberate exposure and intervention
what is natural active immunity
a type of immunity in which the body produces antibodies in response to a normal infection by a pathogen
what is artificial active immunity
the deliberate administration of disabled antigens to elicit the production of antibodies
what is natural passive immunity
a form of immunity in which an individual receives antibodies from a natural means, such as through breastfeeding
what is artificial passive immunity
the administration of antibodies to provide an immediate, specific immune response
