Second line of defence Flashcards
when does the second line of defenece operate
when a pathogen has crossed the first line of defence
what cells does the second line of defence involve
leukocytes - neutrophils, eosinophils, mast cells, macrophages, dendritic cells, natural killer cells
what are the cells that are phagocytes
dendritic cells, macrophages and neutrophils
what do macrophages do
consume and destroy forgein or dead material by engulfing it via endocytosis, have lysosomes contains lysozymes which destroy the forgein/dead material
aside from functioning as phagocytes, macrophages and dendritic cells are also
antigen presenting cells, they contain MHC II markers, on which they present antigens from the consumed material
where are neutrophils found and how do they compare to other phagocytes
most common type of WBC, found in the blood stream and pus
where are monocytes found and how do they compare to other phagocytes
travels through the blood where it eventually migrates into the tissues of the body, here it specialises into macrophage, largest WBC
where are macrophages found and how do they compare to other phagocytes
found everywhere inside the body, aside from function as a phagocyte and antigen presenting cell, they also produce a wide range of chemicals, enzymes, complememnt proteins and regulatory factors
where are dendritic cells found and how do they compare to other phagocytes
found on the surface of body (skin, eyes, mucous membranes), similar to macrophages
function of natural killer cells
upon finding a self cell displaying non-self antigens on its surface, NK cells release a death lignand - a siggnally molecule that stimulates the cell to die by apoptosis
when is a natural killer cell activated
recruited to the sight of infection when infected cells release a cytokine callde interferon, kills cancerous cells or cells infected by a virus
structure of natural killer cell
large granulated cells conatining the killer inhibitory receptor and killer activation receptor
killer inhibitory receptor
examines the surface for MHCI markers, prevents NK cell from killing healthy cell
killer activation reeceptor
binds to certain molecules which appear on ce;;s underhoing cellular stress
where do mast cells reside
in connective tissue, such as under the skin and the connective tissue surrounding blood vessels
what is the process/function of mast cells
when an injury is detected or stimulated by antigens or allergens, they become activated and degranulate, releasing histamines
histamines
molecules that induce an inflammatory response
allergens
a type of antigen that produces an abnormally vigorous immune response to fight off a percieved pathogen
what type of pathogen do eosinophils combat
effective in eliminating multicellular pathogens, secreted when there are skin conditions, allergic reations, autoimmune diseases, certain cancers and bone marrow disorders
what is the function/process of eosinophils
flock to the site of infection, degranulate - secreting histamines and toxic cell mediators, perforating cell mediators and destroying pathogens, not phagocytees so dont engulf
what are the two components of the second line of defence
cellular and non-cellular componenent
two componenets of the non-cellular component of the second line
the complement system and cytokines
cytokines
tiny proteins secreted by cells as a wway to communicate with one another
interferons
type of cytokine that interfere with processes (e.g. viral replication)
when/what are interferons released from
cells infected by a virus
what do intereferons do
alert nearby cepps to reduce their susceptability to infection/heighten their antivirus defencees, promote activation of immune cells, differentitation of immune cells, increase body temp, recruit NK cells, upregulate the production of MHC I markers
where do complement proteins proteins reside
synthesised in the liver and ciirculate in the blood in ann inactive state, is activated when it is cleaved (part of it breaks free)
what are the three outcomes of complement
opsonization, chemotaxis, lysis
opsonization
process by which pathogens are coated with molecules so that they are more easily detected by phagocytes
chemotaxis
the complement proteins gather near the pathogen and attrcact phagocytes to it, making it easier to be destroyed
lysis
complement proteins join together on the surface of pathogens, forming a membrane attack complex (MAC), which creates pores in their membrane destroying the pathogen
