Immunology Overview Flashcards
Edward Jenner and Vaccination
1796 - inoculation with cowpox to protect against smallpox
what is the only disease eradicated by humans?
Small pox
Why does the small pox vaccine work?
Cow pox is a related virus
Innate immune response
Non-specific recognition
No memory
Physical barriers
Secreted components
Proteolytic enzymes
Complement cascade
Ion chelators
Interfons
Phagocytes
NK cells
Adaptive Immune response
Specific recognition
Memory - secondary immune response
T cells (CD4 and CD8)
B cells - antibodies
How is the secondary immune response different from primary?
A shorter or no lag period
More efficient response
More antibodies produced
Antibody concentration remains higher for longer
What cells do common lymphoid
progenitor cells produce?
White blood cells
What cells do common myeloid progenitor cells produce?
Dendritic cells
Granular cells like phagocytes
Red blood cells
Immature dendritic cells …
are highly phagocytic
engulf extracellular fluids
myeloid derived
Granular cells
have granules in the cytoplasm
are short lived
eosinophils
basophils
neutrophils
what is the mast cell progenitor?
unknown
Mature dendritic cells are
the bridge between innate and adaptive immunity
mature dendritic cell are
Specialised at antigen presentation and not really phagocytic
activate T cells
list the 6 myeloid cells
Macrophage
dendritic cells
Neutrophils
eosinophils
Mast cells
Basophils
Myeloid cells are
Primarily secretory cells that can be activated by antibodies
Eosinophils function
kill larger pathogens that cannot be phagocytosed
Basophils are
not fully understood but involved in allergy and parasitic immunity
mast cells secrete
histamine
naive B and T cells..
circulate through the blood and lymph looking for antigens
what happens in the lymph node?
B and T cells are activated
What do H&E stains show?
nucleus in purple
and cytoplasm in pink
Overview of B cells
mature in and derived from the bone marrow
Express immunoglobulin BCR
differentiate into antibody-secreting plasma cells
Overview of antibodies
2 heavy chains and 2 light chains
produced and secreted by b cells
antigen specific variable regions
What is the antibody effector function determined by?
the constant Fc region
What is used as a parameter to measure the immune response?
Antibody levels
what are the 4 effector functions of antibodies?
Neutralise toxins and viral particles
Neutralise adhesion from bacteria
Opsonisation
Complement activation
What does antibody neutralisation do?
Prevent toxins binding to cell receptors
make antigen-antibody complex
engulfed by phagocytes
also used on viruses
What does antibody opsonisation do?
Antibodies bind to and coat bacterial cells
Fc regions then bind to macrophages
bacteria cells destroyed by phagocytosis
What does antibody complement activation do?
antibodies bind to complement proteins to activate the complement cascade to destroy the antibody pathogen complex
“complement antibody function”
Overview of T cells
Derived from the bone marrow but mature in the thymus
express TCR
Recognise foreign antigens on HLA (MHC)
effector T cells
What can effector T cells do?
Help B cells make antibodies
Promote bactericidal activity of macrophages
cytolysis of infected cells
What does CD stand for?
Cluster of differentiation
T helper cells overview
express CD4
Recognise HLA class 2
Release cytokines and help B cells and activate macrophages
T cytotoxic cells overview
express CD8
Recognise HLA class 1
lysis of infected and tumour cells
Do T cells have a secondary response?
Yes
T cell life cycle
- mature in the thymus
- Circulation in search for antigens
- recognise antigen
- clonal expansion
- effector function
- death or a few remain as memory cells
Which cells are antigen-presenting cells?
Dendritic cells
Macrophages
B cells
how do B cells present antigens?
Using HLA class 2 receptors
Why is there such variation in HLA receptors?
genetic polymorphism allows for a massive number of specific receptors to be made
What antigens do B cells recognise?
proteins with folding and conformation
- the antigen
What antigens do T cells recognise?
fragments of the antigen
10ish aa presented by HLA
antibodies often recognise conformational epitopes. what is an epitope?
portion of the antigen that is bound to the antibody
what is a primary lymphoid organ?
a site of major lymphoid Development
What are the primary lymphoid organs?
Bone marrow - lymphoid progenitors and B cell s
Thymus - T cell development
What is a secondary lymphoid organ?
a major site lymphocyte interaction with antigens and other lymphocytes
What are the secondary lymphoid organs?
spleen
lymph nodes
mucosal-associated lymphoid issue: tonsils, BALT and peyer’s patches
What happens in a secondary lymphoid organ?
T cell recognition from dendritic cells
T cells and B cells interacting if they are presenting the same antigen
What development do T cells undergo in the thymus?
positive selection - can recognise HLA
negative selection - self antigens are killed off
Where do pathogens go once detected?
they enter the draining lymph node and naive immune cells interact with antigens and the mature cells enter the bloodstream
why are lymph nodes highly organised?
so the cells sit in different areas and this maximises the interaction between different cells
When are germinal centres present?
during infection
what happens when a dendritic cell (APC) enters the lymph node?
- presents the antigen to the T cell to activate them
- T cells then enter B cell areas to activate them
- cell proliferation
- b cell migration to the medulla and production of antibodies
