Introduction and Phagocytosis. Flashcards
What are the 2 categories of immune cells within the innate immune system?
Sentinel cells.
Phagocytic cells.
What is the function of the sentinel cells of the innate immune system?
They are involved in finding out what the problem is and then alerting the body to that problem.
What happens in the innate immune system once sentinel cells have alerted the immune system that there is a foreign substance in the body?
Phagocytic cells go and remove the thing that is causing the problem.
What are the 3 types of sentinel cells that are found in the innate immune system?
Macrophages (MO).
Dendritic cells (DC).
Mast cells.
What are the 3 phagocytic cells in the innate immune system?
Macrophages.
Sometime dendritic cells.
Neutrophils.
Are natural killer cells part of the innate or adaptive immune system?
The innate immune system.
What is the function of sentinel cells?
To recognise foreign invaders and warn the rest of the immune system.
What is the primary activators of the innate immune system?
The sentinel cells.
The sentinel cells of the innate immune system tend to be in highest concentration at what areas of the body?
At the site of infection or injury.
What cell are involved in detecting parasites or foreign microbes in the tissues?
The sentinel cells.
What allows the cells of the innate immune system to recognise pathogens?
Pathogen recognition receptors (PRR) on the external surface of these cells.
What part of a pathogen is recognised by the PRR of an innate immune cell?
PAMPs (pathogen associated molecular patterns) which are found on the external surfaces of microbes.
What allows cells of the innate immune system to recognise infected host cells?
DAMPs (damage associated molecular patterns).
These are cellular molecules that should be inside a cell, their presence out of the cell indicates damage.
Will an innate immune cell express every type of PRR?
No, they express different PRRs.
What is the major function of mast cells?
They are highly involved in allergy responses and can also trigger inflammation.
What is the major function of macrophages?
To capture and kill microbes and present antigens from pathogenic cells.
What cells of the innate immune system can be considered to be sentinel and phagocytic cells?
Macrophages.
What is the major producing antigen cell of the innate immune system?
Dendritic cells.
Can dendritic cells carry out phagocytosis?
Yes.
Will macrophages and dendritic capture antigens and present them to cells of the adaptive immune system?
Yes.
What cells are often responsible for initiating the first reaction of the adaptive immune system?
Dendritic cells and macrophages.
When are innate immune molecules made?
When sentinel cells are activated.
What are the 3 functions of innate immune molecules?
As pro inflammatory markers.
As inhibitors of microbial growth.
As recruiters of other components of the immune system.
What are cytokines?
Small protein molecules that are secreted by immune cells.
Are cytokines always present in the blood?
Yes.
Will cytokines be released by innate or acquired immune cells?
They can be released by both the innate immune system and the adaptive immune system.
What are the 3 major functions of cytokines?
Regulation of interactions between cells.
They impact the behaviour of cells.
Regulation of the growth and differentiation of cells.
What are the 4 major types of cytokine?
Interleukins.
Lymphokines.
Interferons.
Chemokines.
Are the functions of different classes of cytokines highly restricted?
No, all of the categories overlap meaning that a cytokine that is a lymphokine can also act as an interferon.
What cytokine is in highest concentration in the blood?
Interleukins.
What is the function of interleukins?
They control the growth and differentiation factors of cells in the immune system.
What immune cells secrete lymphocytes?
Lymphokines.
What are the roles of chemokines?
They are pro-inflammatory and chemotactic.
What is the role of interferons?
They affect viral replication and also play a role in regulating immune responses.
What are the 3 ways that all cytokines will act in?
An autocrine manner.
An endocrine manner.
A paracrine manner.
Are cytokines only involved in local immune interactions?
No, they are responsible for local interactions, intermediate interactions and long distance interactions.
The 3 most important cytokines are released by what type of cells?
Sentinel cells.
What are the 3 most important cytokines that are released by sentinel cells?
TNF (tumour necrosis factor).
IL-1 (interleukin 1).
IL-6 (interleukin 6).
What is the role of the 3 cytokines that are released by sentinel cells?
They are responsible for the initial responses to inflammation and they also regulate fever.
Are the cytokines TNF, IL-1 and -L-6 pro-inflammatory cytokines?
Yes.
E.g. During a bacterial infection, once the bacteria have been recognised a macrophage will release all 3 of these cytokines.
What are the 3 main pro-inflammatory effects of releasing TNF, IL-1 and IL-6?
Increased vascular permeability.
Increased blood flow.
Attraction of neutrophils to the injury/infection site.
What are the 2 main phagocytic cells?
Neutrophils.
Macrophages.
What are monocytes?
Derivatives of macrophages that are always found in the blood.
Where do monocytes carry out phagocytosis?
In the blood.
Where do macrophages carry out phagocytosis?
In the tissues.
Are dendritic cells phagocytic?
Yes, but they phagocytose to present antigens rather than to kill a pathogen.
What are the 5 soluble defence factors that are involved in phagocytosis?
Enzymes.
Defensins.
Interferons.
Cytokines.
Complement proteins.
How do enzymes help with phagocytosis?
They cause oxidative damage to cell membranes.
How do defensins help with phagocytosis?
They contain anti-bacterial peptides.
How do interferons help with phagocytosis?
They can interfere with viral replication.
What cells produce interferons?
Phagocytes and other cells.
What cells produce compliment proteins?
Macrophages and hepatocytes.
What are the 3 main tasks of compliment proteins?
Cell lysis.
Chemotaxis.
Opsonins.
How do complement proteins kill foreign cells or infected cells?
Via cell lysis.
How do complement attract other pro-inflammatory cells to areas of infection?
They use chemotaxis to form a chemical gradient which attracts other inflammatory cells to the site of infection.
Can complement proteins perform opsonistation?
Yes.
How do complement proteins perform opsonisation?
They coat microbes in molecules called opsonins which mark these microbes for phagocytosis.
What receptors are found on most phagocytic cells?
PRR receptors.
How do PRR receptors help with phagocytosis?
They bind to PAMPs on the microbes.
Are intergrins found on the surface of phagocytic cells?
Yes.
What is the role of the intergrins on the surface of phagocytic cells?
They allow neutrophils to attach to the endothelium at the area of infection.
How do neutrophils attach to the endothelium at the site of infection?
Once they reach the site of infection they will use their intergrin to attach to the endothelium.
What are leukocyte adhesion molecules?
A class of intergrin that are present on almost every leukocyte.
What are the 4 main steps of phagocytosis?
Chemotaxis.
Adherence.
Ingestion.
Destruction.
What is chemotaxis?
The directed movement of cells down a chemical gradient.
What are 3 things that usually form a chemical gradient?
Microbial protein molecules.
Complement proteins.
Chemokines.
What do chemotactic gradients help immune cells to do?
To get to an area of inflammation.
What is the most common chemotactic gradient?
IL-8.
Innate immune cells have receptors for what 2 soluble proteins?
Complement proteins.
Antibodies.
What part of the antibody will innate immune cells bind to?
The FC region.
What are opsonins?
Soluble proteins that are used to coat pathogens so they can be recognised by a phagocytic cell.
Neutrophils and monocytes have receptors for what 4 things?
Soluble proteins.
Complement proteins.
The FC part of an antibody.
PAMPs on microbes.
What part of a microbe will complement proteins bind to?
To antigens on their cell surface.
Why do complement proteins bind to immune cells?
So other immune cells can recognise the microbe so it can be destroyed.
What region of an antibody binds to the pathogen?
The FAB region.
How do antibodies lead to pathogen destruction?
They use their FAB region to bind to pathogens.
Immune cells bind to the FC region and destroy the cell.
Will antibodies bind to pathogens that the body has never seen before?
No.
How do immune cells bind to pathogens that the body has never seen before?
They must bind to PAMPs.
Can complement proteins bind to pathogens that the body has never seen before?
Yes.
What happens once a phagocyte has ingested a foreign cell?
It is destroyed.
What are the 2 ways that phagocytes kill ingested cells?
Oxygen dependent killing.
Oxygen independent killing.
What organelles mainly carry out oxygen dependent killing?
The lysosomes.
What usually carries out oxygen independent killing?
Substances with a very low pH, proteases, DNAse’s and RNAse’s.
Can some pathogens survive inside a phagosome?
Yes.
What are 5 common pathogens that can live inside a phagosome?
Mycobacterium bovis.
Rhodococcus equi.
Brucella abortis.
Lysteria monocytogenes.
Salmonella typherium.
What is the phagosome?
The complex that is formed when a pathogen is ingested by a phagocyte.
