Immunology Flashcards
what are the 3 layers of defence our immune system has?
- physical barrier
- innate arm of immune response
- adaptive arm of immune response.
what are some physical barriers of the immune system?
skin, nails, epithelial, mucosal layers.
what are lysozymes in saliva most effective against?
most effective against gram +ve bacteria
how do lysozymes preform their function in the oral cavity?
they cleave the chemical bonds between sugars on the peptidoglycan layer of bacteria, enabling other microbial agents to destroy the lipid bilayer around bacteria.
how do antimicrobial peptides preform their function in the oral cavity?
attack the exposed lipid bilayer around bacteria.
what are some antimicrobial peptides found in the oral cavity?
- Defensins
- Cathelicidins
- Histatins
what is the purpose of defensins in the oral cavity?
several can insert into the lipid bilayer of bacteria, creating a pore - allowing the content to leak out.
what is the purpose of cathelicidins in the oral cavity?
cause membrane disruption.
what type of cathelicidins are found in humans?
LL-37
what is the purpose of histatins in the oral cavity?
fight fungal pathogens
what produces histatins?
salivary glands.
what kind of receptors are found on innate arm response cells?
genome encoded receptors.
which arm of the immune system has lasting protection?
adaptive responce.
what is the purpose of the innate arm?
provide initial defence, limiting pathogen proliferation and spread.
How long does it take the adaptive arm to start?
up to 4 days.
why do the cells of the adaptive arm have a vast range of receptors? and what does this mean?
- as the receptors are not genome encoded so receptor recognition improves.
why does the adaptive arm need to be more potent?
to control more virulent pathogens,
why does the adaptive arm take longer?
because it has to be started by the innate response. And it takes time to raise population of cell specific for pathogen.
what is the complement system?
plasma that ‘complemented’ the killing of bacteria by phagocytes.
what are the functions of complement?
- facilitate recognition of bacteria by phagocytes.
- directly lyse bacteria.
what is the classic pathways that the complement system can be activated?
when C1 interacts with a pathogen surface or binds to antibodies bound to the surface. has C1q (recognition component) and C1r+C1s (proteases) - these 3 form C1 complex.
what is the alternative pathways that the complement system can be activated?
C3 undergoes spontaneous hydrolysis - forming a complex with factor D,P,B producing C3bBb complex (C3 convertase)
what is the lectin pathways that the complement system can be activated?
lectin like molecules do the recognition and ficoline bind carbs on pathogen surface leading to C3 convertase.
what do all compliment pathways generate?
C3 convertase.
what is the purpose of C3 convertase?
cleaves C3 - leaving C3b bound to microbial surface and releasing C3a.
The C3b then starts the release of C5a.
How do C3a and C5a aid in the immune response?
they recruit phagocytic cells to the site of infection and promote inflammation,
what is the purpose of compliment leaving C3b on the surface of the pathogen?
phagocytes with receptors for C3b with come and engolf + then destroy the pathogen.
what does completion of the complement cascade lead to?
formation of a membrane-attack complex (MAC) - which disrupts cell membrane and causes cell lysis.
what is a zymogen?
an inactive form of an enzyme, usually protease, that must be modified in some way (eg cleaved in a particular site) to become active.
where are immune effector cells derived from?
common pluripoten progenitor cell types in bone marrow
after a stem cell divides in the bone marrow, the daughter cells can either differentiate or divide - what happens if they differentiate?
they mature. This then restricts their potential and they lose the ability to self renew.
after a stem cell divides in the bone marrow, the daughter cells can either differentiate or divide - what happens if they divide?
they continue being a stem cell.
where do the adaptive effector cells come from?
a lymphoid and myeliod path in the bone marrow.
where do the innate effector cells come from?
a lymphoid and myeliod path in the bone marrow.
what are the adaptive effector cells?
- B cells
- Plasma cells
- T cells
- Activated T cells.
what are the lymphoid innate effector cells?
Natural Killer Cells and Activated Natural killer cells.
what are the myeliod innate effector cells?
- Granulocytes
- Mast cells
- Macrophages
what is the function of a macrophage in the innate immune response?
- 1st responders .
- phagocytosis.
- remove dead cells and debris.
- draw in other immune cells
- present antigen from phagocyte on its surface for T cells.
(killers nad whistle blowers)
What are granulocytes?
polymorphonuclear leukocytes, (neutrophils)
what is the function of neutrophils in the innate immune response?
- Phagocytic
- Bactericidal
(many killer soldiers)
what is pus?
dead neutrophils
where are neutrophils located?
in the blood.
where are macrophages located? (mature and immature)
mature = most tissues in submucosal layers.
immature = in blood.
what is the function of dendritic cells in the innate immune response?
phagocytosis. - to then present the antigen to the adaptive arm - activating the adaptive arm.
(transporter)
what is the function of Natural killer cells in the innate immune response?
release cytotoxic granules. These can damage host cells .
they look for cells that are infected with a virus or a tumour.
where are dendritic cells located? (mature and immature)
immature = under surface epithelial and in solid organs.
Once they phogolose a pathogen they move to the lymph nodes and mature.
where are natural killer cells located?
blood.
what cells can phagocytose?
- macrophages
- neutrophils
- Dendritic cells.
what are the receptors that are found on phagocytic cells that start an immune response?
- Fc receptors.
- complement receptors. (recognise C3b)
- Pattern recognition Receptors (PRR)
what are PAMPS?
Pathogen associated molecular patterns that are found on pathogens.
what are the 3 types of PAMPS?
- Lectin Like
- Scavenger receptors
- Toll like receptors.
what are the stages of phagocytosis?
- bacterial binds to receptor on cell surface
- endocytosis (engolfing) of the bacterial into the cell
- this created a membrane bond vesicle in the cell. (phagosome)
- lysosomes fuse with the phagosome forming the phagolysosome - they inject toxic material breaking and killing it.
what is the function of toll like receptors?
to recognises a distinct set of PAMP not found in vertebrates.
why are toll like receptors important?
in preventing fungal infections.
how do phagocytes prevent bacterial growth and kill some?
pH is very low.
what are the antimicrobial mechanisms of phagocytes?
- pH very low
- Respiritory burst (cause cells stimulated to produce lots of toxic o2 species and toxic nitrogen species which damage the engulfed microbes.
- Phagocytes stimulated to reases anti-microbial peptides (cathelicidin)
- produce decretive enzymes (lyzsozyme)
what is a cytokine?
a small protein that affects the behaviour of other cells.
what is chemokine?
small chemoattractant protein that draws cells to where they are needed.
during the immune response what cells initiate inflammation?
macrophages and complement.
when macrophages engulf the bacterial what is triggered to be released?
cytokine (eg IL-1 and chemokine)
what makes the blood vessels in the infected areas more permeable and why?
- cytokines.
- they make it more permeable meaning that neutrophils can come out more easily. It also allows more plasma to leave the blood. (increasing complement proteins for clotting factors and phagocytosis)
what are the purposes of cytokines in the innate immune response?
- make blood vessels more leaky
- tell neutrophils where they need to go.
what cells initiate the adaptive immune response?
dendritic cells.
what is the difference between PAMPS and specific antigen?
specific antigens are only for one receptors where as PAMPs are for many.
what happens to B and T cells once they mature?
have their own unique specificity for antigen.
where do B cells mature?
in the bone marrow
where do T cells mature?
in the Thymus
why only once a cell with a specific antigen for the infected pathogen does it undergo colonal expansion?
because there isn’t enough room in the blood for every single possible cell with a unique antigen for everything.
what are left behind when the infection is cleared and why do the other cells die?
Memory cells. The other die to allow for enough room for other cells to fight a different infection.
what mechanism allows us to fight infection within the limited space we have in the blood?
constant colonal expansion and retraction periods so there isn’t loads of these cells in the blood system at one time.
what is a problem with receptors in B/T cells being randomly generated?
we make some that are self reactive.
where are self reactive cell receptor cells removed?
either in the bone marrow or in the thymus.
what are the 2 cells that B cells can differentiate into?
- effector cells that can produce the antigen
- memory cells.
what are the 2 cells that T cells can differentiate into?
- effector cells
- memory cells.
what do B cells mature into?
Plasma cells.
what is the function of plasma cells?
can release their receptors and bind to a specific antigen alone.