PoH: Foundations of Immunology Flashcards
Define immune system
The body’s ability to resist or eliminate pathogens (potentially harmful foreign material)
Define immunity
Protection from infectious diseases
Define pathogen
Any microorganism that causes harm
What 4 cells are part of innate cellular immunity?
Phagocytes
Eosinophils
Mast cells
Basophils
What 2 features of innate immunity are humoural?
Complement and cytokines
Define innate immunity
Ability for our IS to take action as soon as a pathogen will infect our body
What are the 3 features of innate immunity?
Doesn’t differentiate between types of pathogens
Fast and immediate
No memory
Define acquired immunity
Stimulated by exposure to a microbe
Name the 3 features of acquired immunity
Distinguishes between different pathogens based on antigens
Slow - can take a few days to develop
Immunological memory
What cells are involved in adaptive immunity?
B lymphocytes
T lymphocytes
Name the 3 types of T-cell
Memory T - remember antigens presented by MHC
Helper T - stimulate B cells to make antibodies
Cytotoxic T - kills pathogens
Where are T cells made and trained?
Made in bone marrow
Trained in thymus
Name the 4 types of Helper T cell and what they target
TH1 - targets macrophils
TH2 - targets eosinophils
TH17 - targets neutrophils
TFH - targets B cells
What do Natural Killer cells do?
Destroy infected/diseased cells
What do B cells do and where are they trained?
Involved in production of antibodies
Have B cell receptors
Made/trained in bone marrow
What 2 types of B cell are there?
Memory B cell
Plasma B cells
Vaccines lead to what type of cell formation?
Memory B cells
What do Plasma B cells do?
Produce antibodies and immunoglobin
Name the 4 cells from myeloid lineage
Platelets
Erythrocytes
Phagocytes
Basophils
Name the 3 types of phagocyte
Neutrophil
Mast
Monocyte
What 3 things to neutrophils release?
Peroxidases
Alkines
Acid phosphates
What do mast cells release?
Histamine
What pathology are mast cells associated with?
Allergy
What percent of WBCs are monocytes?
5%
Name the 2 types of monocyte
Macrophage
Dendritic
Define complement
Not cells. They’re plasma proteins that can be activated directly against pathogens, leading to the complement cascade
What 6 external barriers do we have to stop pathogens invading?
Skin
Mucus
Saliva/tears - contains lysozomes
Urine
Sweat - high NaCl, lysozomes
Stomach - pepsin and gastric acid
Name the 6 steps of phagocytosis
- Attachment of phagocyte to pathogen
- Ingestion of pathogen
- Formation of phagosome
- Phagosome fuses with lysosome
- Destruction of pathogen and formation of residual body
- Elimination of waste materials
What 3 things are eosinophils involved in?
Parasitic infection
Allergy
Asthma
What type of cell are mast cells, what process are they involved in and what immunoglobulin do they have?
Eosinophil
Type 1 hypersensitivity (allergy)
IgE
Define cytokine
Small proteins secreted by immune and non-immune cells if there’s a stimulus
What 3 things do cytokines do?
Communicate to each other
Bind to specific receptors producing signalling molecules
Innate and acquired immunity - differentiation, activation, chemotaxis, enhancing cytotoxicity
What 3 things does the lymphatic system do?
Drain tissue
Absorb/transport fatty acids and fats
Immunity
In what 3 ways does the lymphatic system play a role in immunity?
Recognition of danger
Production of specific weapons
Transport of weapons to attack site
What are the two types of primary lymphoid organ?
Bone marrow - where T/B cells are made and where B cells receive training
Thymus - for T cell training
What are the 4 types of secondary lymphoid organs
Lymph nodes
Tonsils and adenoids
Spleen
Peyer’s patches
How many grams is the spleen and where is it?
150g
Left upper quadrant
What types of pulp does the spleen have and what do they do?
Red pulp - filters blood by removing damaged/aged blood cells and microbes
White pulp - mainly lymphocytes
What does the thymus’s medulla and cortex contain?
Medulla - immature T cells and macrophages
Cortex - mature T cells
What is a Peyer’s patch?
Mucosal immune system
Where are T and B cells produced?
Bone marrow
Where are T and B cells trained, and what do they express?
T cells - TRC in thymus
B cells - BRC in bone marrow
Define the function of lymphoid organs
Lymphoid organs filter and trap invading pathogens and present them to immune competent cells
What do Cytotoxic T cells do? What receptors do they have? When do they recognise antigens?
Kills pathogens
Has CD8+ receptors
Only recognises antigens whne bound to MHC I
What do Helper T cells do? What receptors do they have? When do they recognise antigens?
Stimulate B cells to produce antibody. They can’t kill but activate and direct other immune cells
Has CD4+ receptors
Only recognises antigens bound to MHC II
What do TH1 target?
Macrophages via macrophage activation
They defend against pathogens, and play a role in autoimmunity and chronic inflammation.
What do TH2 target?
TH2 targets eosinophils via eosinophil/mast cell activation.
They defend against helminths (worms) and play a role in allergy.
Th1. Name:
- Principle target cell
- Major immune reaction
- Host defence
- Role in disease
Macrophages
Macrophage activation
Intracellular pathogens
Autoimmunity, chronic inflammation
Th2. Name:
- Principle target cell
- Major immune reaction
- Host defence
- Role in disease
Eosinophils
Eosinophil/mast cell activation
Helminths
Allergy
Th17. Name:
- Principle target cell
- Major immune reaction
- Host defence
- Role in disease
Neutrophils
Neutrophil recruitment and activation
Extracellular bacteria and fungi
Autoimmunity, inflammation
Tfh. Name:
- Principle target cell
- Major immune reaction
- Host defence
- Role in disease
B cells
Antibody production
Extracellular pathogen
Name the 3 steps in T-cell interactions
- Cytotoxic T cell binds to infected cell
- Perforin makes holes in infected cell’s membrane and enzyme enters
- Infected cell is destroyed
What chemical do Cytotoxic T cells use to make holes in the infected cells membrane?
Perforin
Where is MHC I found, what does it present and trigger?
Virtually all nucleated cells
Presents ‘virally induced’ peptides to CD8+ T cells
Triggers cytotoxic response
Where is MHC II found, what does it present and trigger?
Found on Professional Antigen Presenting Cells (APCs, i.e. macrophages)
Presents exogenously produced Ag to CD4+ T cells
What MHC can macrophages express?
MHC I and MHC II
What two pathways do macrophages use?
Endogenous pathway - virus proteins
Exogenous pathway - pathogen swallowed, becomes phagosome, and MHCII with the antigen is presented to helper T cells
Describe the endogenous pathway of antigen presentation
Viral proteins
Proteasome
TAP into ER
MHC I
Antigen presentation to CTLs
Describe the exogenous pathway of antigen presenetation
Extracellular pathogen
Phagosome
MHC II
Antigen presentation to helper T cells?
Can pathogens from the endogenous pathway cross over to the exogenous pathway?
No.
But pathogens from the exogenous pathway can head to the ER for antigen presentation. This is cross-presentation
What do B cells do?
They have antigen receptors on their surface
Produce antibodies
What are antibodies?
Proteins produced as a response against antigens
What 2 parts do antibodies have?
Antigen binding region - interact with antigen
Fc region
Name the 4 types of antibody
igM
IgA
IgE
IgD
IgG
Which antigen is produced at the first sign of infection? What’s its affinity like?
IgM
Low affinity
High voracity
What does IgA protect?
Mucosal surfaces
What does IgE relate to?
Allergies and parasites
What does IgD do?
Non-functional
What type of antibody is most common?
IgG
What does IgG bind with
Bacteria, fungi and infection
What 3 things do antibodies do?
Neutralisation – prevent attachment and entry. This is mostly IgA, in GI tract and respiratory tract
Opsonisation – antibodies recognising antigen expressed on the pathogen and making it more attractive to macrophages
Complement activation – mostly through the classical pathway
How many proteins/factors make up the complement system?
Over 30
Where does activation of the complement system occur?
On the surface of target cells
Activation happens in a cascade-like format
What is Membrane Attack Complex?
A pore on the surface of an infected cell.
The result of proteins undertaking auto cleavage and using an enzyme to change the shape of subunits to become more active
What are the three main pathways of the complement system?
Classical pathway
Alternative pathway
Lectin pathway
What 3 functions do complement have?
Lysis of infected cell
Chemo-attractants
Phagocytosis via opsonisation
Define active immunity
Transfer of antibodies or lymphocytes specific to the microbe, e.g. recovered from COVID
Define passive immunity
individuals who have not yet encountered a particular antigen are immune/protected, e.g. not had COVID but injected with antibodies
Describe active immunity, its mechanism, its time, whether there are B memory cells and how long it lasts
Recovered from illness
Own IS involved in producing antibodies
Takes weeks to develop
Present
Permanent/long term
Describe passive immunity, its mechanism, its time, whether there are B memory cells and how long it lasts
Not infected but injected with antibodies of recovered person
Transfer of antibodies/cells from others
Immediate
Absent
Temporary/short term
Define susceptible or naïve immunity
individuals who have encountered a pathogen and are protected from subsequent encounters via antibodies. They are immune/protected.
