7c- second line of defence Flashcards
what are phagocytes?
Phagocytes are cells that perform phagocytosis, consuming and destroying foreign or dead material, engulfing it through endocytosis
what are the cellular components of the second line of defense?
all of the cells involved in second line of defence are known as leukocytes or white blood cells
what happens once the dead material is engulfed by phagocytes?
once engulfed, lysosomes within the phagocytes, which contain antimicrobial enzymes called lysozymes, fuse with the vesicles containing the material and destroy it
what is a neutrophil?
most common type of leukocyte in the body. Engages in phagocytosis of pathogens and foreign material, as well as the release of cytokines
what are macrophages and dendritic cells?
a type of leukocyte that engages in phagocytosis and antigen presentation, also known as antigen presenting cells (APC’s). They consume and destroy foreign material as well as present antigens from the consumed material on their surface.
what do macrophages and dendritic cells stimulate?
stimulate specific immune response
what are antigen presenting cells?
APC’s are specific cells that express MHC class II to display consumed antigens on their surface, enabling interaction with the adaptive immune system.
how do phagocytes communicate within the immune system?
phagocytes release a number of substances such as cytokines, which are important cell signalling molecules which help protect against pathogens and help guide immune cells to the site of infection or injury, allowing them to function optimally.
what are cytokines?
cell signalling molecules which help protect against pathogens and help guide immune cells to the site of infection or injury, allowing them to function optimally.
what are natural killer cells?
Natural killer cells are a type of leukocyte responsible for the recognition and destruction of damaged and/or infected host cells.
How do natural killer cells achieve their job?
They achieve it with the help of 2 receptors called killer inhibitory receptor and killer activation receptor
what is the killer inhibitory receptor?
examines surface of cells for MHC class I markers
what is the killer activation receptor?
binds to certain molecules which appear on cells undergoing cellular stress
how can presence of MHC class I markers be altered?
due to various disease processes. Viral infections either destroy or suppress production of MHC Class I markers, leading to their absence
when is cell death initiated?
Cell death is initiated only in infected or abnormal cells that lack a sufficient MHC Class I markers.
what is the role of the two receptors in the scenario of cell death?
The killer inhibitory receptor is unable to bind to enough MHC class I markers as the presumed cell about to undergo cell death lacks a sufficient number of MHC Class I markers and thus the killer inhibitory receptor is unable to inhibit the cell death signal. This activates the killer activation receptor, initiating cell death.
when does cell death NOT occur?
if killer inhibitory receptor detects a sufficient number of MHC Class I markers, it overrides the killer activation signal, preventing cell death.
where do mast cells reside, and what is the role of mast cells?
Mast cells reside in connective tissues throughout the body. Their role is to become activated and degranulate to release histamine when they detect injury to surrounding cells or are stimulated by antigens or allergens.
What is the effect of histamine on the body?
Histamine has several effects on the body and plays a crucial role in the inflammatory response
what are eosinophils?
Eosinophils are large granulated cells containing various toxic chemical mediators such as DNases, RNases and proteases, which help destroy invading pathogens.
what is the role of eosinophils?
The role of eosinophils is that they typically target pathogens which are too large to be phagocytosed by dreganulating on contact with them and releasing the chemical mediators contained within their granules
what are the cellular components of the second line of defence?
phagocytes (neutrophils, macrophage and dendritic cells), natural killer cells, mast cells and eosinophils
what are interferons?
a type of cytokine
when are interferons released?
when a cell is infected with a virus
how do interferons make infected cells less susceptible to viruses?
interferons interact with receptors on neighbouring cells, inducing changes that make these cells less susceptible to viral infection. this mechanism helps prevent the virus from spreading between cells.
what are complement proteins composed of?
composed of proteins synthesised in the liver
what do complement proteins form?
They form the complement system.
what do complement proteins do in the presence of certain pathogens?
these proteins interact in a series of reactions known as the complement cascade.
what do complement proteins do in opsonisation?
complement proteins stick on the outside surface of pathogens and make it easier for cells of the immune system, such as phagocytes, to recognise them as foreign.
what happens in chemotaxis?
complement proteins gather near a pathogen and attract phagocytes to it, making it more likely to be destroyed.
what happens in lysis?
Complement proteins can join together on the surface of pathogens to form a membrane attack complex (MAC). This complex creates pores in the pathogens membrane, causing lysis by allowing a sudden influx of fluid, which ultimately leads to the pathogen bursting.
What is a fever?
A fever is a temporary increase in body temperature.
what happens during the fever response?
the body initiates countermeasures to increase core body temperature, such as shivering and heat conserving behaviours like putting on a jumper.
what does the innate response of fever help combat?
helps combat potential infections, as many pathogens cannot survive at elevated temperatures
what do fevers do to the immune system?
they bolster the immune system by activating certain proteins that enhance the body’s defences.
how can prolonged fevers be harmful?
due to the additional stress on cells, which do not function optimally at higher temperatures.
What happens during the inflammation response?
the process of inflammation increases blood flow to an injured area, bringing more immune cells and components to clear debris and fight pathogens.
what are the signs of inflammation and what causes it?
an influx of blood and fluid causes swelling, causing swelling, pain and heat.
what does the immune response aim to eliminate?
it aims to eliminate effects pf injuries, defend against pathogens, clear out damaged or destroyed cells and initiate repair.
what is special about the immune response?
it is complex, non specific, occurring the same way regardless of pathogen or injury.
what are the three stages of the immune response?
initiation, vasodilation, and migration.
what might happen for initiation to begin?
an injury may pass through the first line of defence, damaging cells and introducing pathogens such as bacteria into the body.
what would the entry of pathogens during initiation lead to?
this would cause macrophages situated in the tissue to become activated and along with damaged cells, release cytokines. Mast cells would also degranulate, releasing histamine.
what happens to the histamine released from mast cells during vasodilation?
histamine released from mast cells travels to nearby blood vessels and binds to specific receptors, causing vasodilation.
what does vasodilation do?
The increasing of blood vessels increases blood flow to the injury site, leading to the swelling, redness and warmth commonly associated with inflammation.
What happens additionally during vasodilation and what does it do immune system cells??
Additionally, formation of gaps in the vessel walls increases their permeability to immune system cells, allowing those cells to access the affected area more easily
what happens during migration?
Vasodilation and increased leakiness of blood vessels allow several innate immune system components to leave the blood stream and enter the site of injury.
what components are involved during migration?
phagocytes and complement proteins
what is the role of phagocytes in migration?
macrophages and neutrophils are guided to the injury site by cytokines secreted by activated macrophages and damaged cells. At the site, they phagocytose pathogens and digest them using enzymes like lysozomes.
what is the role of complement proteins in migration?
these proteins are attracted to pathogens and facilitate their destruction by making it easier for phagocytes to eliminate them
why does pus come out of an injured area?
its caused by increase in blood flow and immune cell activity.
what does pus contain?
it contains dead immune cells and pathogens
