Immune System 1 Flashcards
Immune system is..
The whole of the cells dedicated to the defence collectively.
An immunogen is…
A molecule that stimulates the immune system to produce a response
Antigen is…
The part of the immunogen that reacts with immune effector cells or soluble antibodies.
An epitope is…
The part of the antigen that reacts with immune effector cells or soluble antibodies.
4 main types of pathogens
Bacteria
Viruses
Fungi
Parasites
Two types of parasites
Protozoa and warms
Components of immune system : (4)
WBC
RBC
plasma
Platelets
Where are blood cells produced?
In the bone marrow
Pluripotent hematopoietic stem cell
Brief process of Haematopoiesis (3)
- pluripotent hematopoietic stem cell produces a common lymphoid progenitor
- produces B cell, T cells and Nk Cells which are then activated.
- B cell becomes plasma cells
T cells become activated
NK become activated
Antigen presenting cells (4)
- monocytes
- macrophages
- dendritic cells
- mast cells
Granulocytes (3)
- neutrophil
- eosinophil
- basophil
Function of
Macrophages and Neutrophils
Phagocytosis and activation of bactericidal mechanisms
Macrophage - antigen presentation
Function of
Dendritic cells
Antigen presentation
Function of
Eosinophil
Killing of antibody coated parasites
Function of
Basophil
Promotion of allergic responses and augmentation of anti-parasitic immunity
Function of
Mast cell
Release of granules containing histamine and active agents
How do we class lymphoid cells?
Small lymphocytes - B cells and T cells
Large lymphocytes - NK cells
Role of NK cells
Kills cells infected with viruses
Role of small lymphocytes
Production go antibodies (B cells) or cytotoxic and helper functions (T cells)
Role of plasma cell
Fully differentiated form of B cell that secretes antibodies
60% of cells in immune system are…
Granulocytes
7% of cells in immune are…
33% of cells in immune are..
7% monocytes
33% lymphocyte
Where can immune cells be found?
Lymphoid organs
Primary lymphoid organs … (2)
Bone marrow
Thymus
Secondary lymphoid organs… (6)
Spleen
Adenoids
Tonsils
Appendix
Lymph nodes
Peyer’s patches
Describe bone marrow
Soft spongy, highly cellular tissue that fills the internal cavity of bones
What originates and matures in the bone marrow?
On the contrary…
B cells originate and mature in bone marrow
T cells originate but leave at an immature stage
Where is thymus located?
Just above the heart
What cells migrate into thymus? And why?
Immature T cells migrate in thymus to complete their maturation
After T cells go to the thymus and differentiate, where do they go?
From the cortex into the medulla.
Do any immune responses happen in the primary lymphoid tissues?
Lymphocytes are only produced and matured here.
No immune responses happen.
What could happen in the secondary lymphoid tissue?
Immune response
Lymph nodes lie…
At the junctions of a network of lymphatic vessels
Lymphatic vessels originate in…
The connective tissues throughout the body where they collect the plasma fluid that continually leaks out from blood vessels.
What is the plasma fluid called that leaks out from the blood vessels?
Lymph
How does the lymph return to the blood vessels after leaking?
Via the thoracic duct
How do lymphocytes arrive into the lymph nodes?
How do they leave?
From the afferent lymphatic vessels
Leave the same way if no pathogens present
What happens if the lymphocytes grow in number in the lymph node?
The lymph node increases in size - this is why people may have swollen glands.
What happens in the lymph nodes if there is a pathogen?
Pathogens are drained in lymph nodes from the afferent lymphatic vessels where they are trapped by dendritic cells and macrophages
B & T cells meet the pathogen and are activated, undergo clinal expansion and differentiation.
What’s another secondary lymphoid tissue?
MALT
mucosa assosciated lymphoid tissue
2 types of immunity
Innate immunity
Adaptive immunity
Features of innate immunity (4)
Rapid response
No memory
Limited specificity
Constant during response
Features of adaptive immunity (4)
Slow response
Memory
Highly specific
Improve during response (don’t stay constant like in innate)
Cells involved in innate immunity
Granulocytes
Neutrophils, eosinophil, basophil, monocytes, NK cells
Cells involved in adaptive immunity
B cells and T cells
What 2 cell types can we not classify as being part of innate / adaptive immunity?
Macrophages
Dendritic cells
Act as a bridge and can be a part of both types of immunity
Phases of immune response (3)
Immediate innate immune response 0-4 hours
Induced innate immune response
4hrs - 4 days
Adaptive immune response
4 days until defeat
Innate immune response is made up of… (3)
Barriers
Antimicrobial peptides
Complement system
3 types of barriers:
With Example for each
Mechanical - epithelial cells joined by tight junctions
Chemical - salivary enzymes (lysozyme)
Microbiological - normal flora on skin in gut
Anti-microbial peptides (4)
Defensins
Cathelicidins
Histatins
Lectins
What is the most important anti microbial peptide and why?
Defensins because they have action against all of pathogens.
What is a complement system?
A group of nearly 30 serum and membrane proteins - act in an orderly sequence.
Roles of complement system:
Opsonisation - they can bind to bacteria allowing them to be phagocytosed by cells with complement receptors ‘by making them more tasty’
2 different pathways of complement system:
Classical Pathway
Alternative Pathway
Describe the classical pathway:
It is both antibody dependent and independent.
What do we mean by antibody dependent or independent?
Can bind to an antigen directly
or
can bind to an antibody which has already binded to an antigen
Describe the alternative pathway:
Classical pathway dependent and completely independent.
Most important opsonin in alternative pathway:
C3b opsonin
Most important opsonin in classical pathway:
C4b opsonin
How to inactivate the complement system? (2)
Using EGTA which blocks calcium - calcium drives the system.
- 56 degrees heating
Why would we want to inactivate the complement system?
During transplants because they cause transplant rejection.
Roles of the complement system: (3)
- some products activate B cells
- some small fragments recruit phagocytes to the site and regulate the inflammatory response.
- opsoning bacteria
What happens during the induced innate immune response? (4)
- phagocytosis
- cytokines production and inflammation
- toll like receptors activation
- NK
What type of cells do phagocytosis? (2)
Neutrophils
Mononuclear phagocytes (monocytes and macrophages)
Differences between neutrophils and mononuclear phagocytes? (2)
- neutrophils are shorter lived unlike mononuclear
- mononuclear are also antigen presenting
What happens in engulfment?
Engulfment - after a particle is bound to phagocyte receptors, forms a phagosome that encloses the particle. This then fuses with a lysosomal granite.
The efficiency of phagocytosis is greatly enhanced when..
the microbe is coated with opsonin proteins which the phagocytes express high affinity receptors.
How does killing/degradation of pathogens occur? (2)
Reactive oxygen species and reactive nitrogen species derived from NO.
or by lysosomal enzymes.
What are cytokines?
Low molecules weight proteins secreted by cells that stimulate or inhibit the activity, proliferation or differentiations of other cells.
How many cytokines are there?
Around 20
Subgroups of cytokines: (4)
interferons
lymphokines
interleukins
chemokine
Some cytokines are mediators and regulators of innate immunity…
where are they produced?
- by monocular phagocytes in response to infectious agents.
Some cytokines are mediators and regulators of adaptive immunity…
where are they produced?
- by T lymphocytes in response to specific recognition of foreign antigens
Some cytokines are stimulators of haematopoiesis
where are they produced?
- by bone marrow stroll cells, leukocytes and other cells and stimulate the growth and differentiation of immature leukocytes.
Cytokines produced by macrophages do 2 things…
IL-1, IL-6, TNF induce fever to decrease bacterial/viral replication
Induce a state of inflammation at the site of the infection.
Features of inflammation (3)
vasodilation
increased vascular permeability
leucocyte migration
What is the aim of inflammation?
To bring immune cells in the location of the infection.
