3 - Immune system II: Adaptive Immunity Flashcards
innate immune system
- Non-specific
- Elements present at birth
- Effective against a wide range of pathogens
- Lifelong presence
- Present in all animal species
adaptive immune system
- Specific for certain antigens
- Gained after exposure to foreign material
- Delay before effective - 5-6 days to respond
- Memory - faster response to subsequent exposure to same pathogen
- Carried out by Lymphatic system
- Only in vertebrates
- Once acquired, it is lifelong (mostly)
cells involved in innate immunity
- innate lymphoid cells
- natural killer cells
- mast cells
- eosinophils
- neutrophils
- macrophages
- dendritic cells (APCs)
APCs
Cells that possess MHC class 2, allows them to activate B and T cells
Cells involved in adaptive immunity
- lymphocytes
- CD4+ T helper cell
- CD8+ Cytotoxic T cell
- B cell
Lymphocytes
- 6 micrometer diameter
- short lifespan
- circulate in blood and lymph
- activated by antigen
- both originate in bone marrow
How do immune cells find one another in the body?
through the circulatory and lymphatic system
where are lymphocytes made?
primary lymphoid organs:
- Bone marrow (b cells mature)
- Thymus (t cells mature)
how do immune cells find pathogens, and each other
- interstitial fluid bayhes tissue and along with blood cells enters the lymphatic vessels
- lymph flows through lymphatic vessels throughout body
- within LNs, pathogens and particles in the lymph encounter and activate APCs
- LVs return lymph to the blood via 2 large ducts that drain into veins
What are the secondary lymphoid organs?
spleen and lymph nodes
what is the role of the lymph nodes?
They filter lymph.
what is the role of the spleen?
filters blood
humoral response role
defends against pathogens and toxins in extracellular fluid
cell-mediated response role
defend against infected cells, cancer cells and transplanted
antigen
any foreign molecule which is specifically recognised by lymphocytes and elicits a response by them
how do lymphocytes detect antigen?
by the B and T cell receptors embedded in their respective membranes, as each is specific for 1 epitope
b cell activation - humoral response
- Developing B cells undergo a selection process in bone marrow: self-reactive cells are destroyed
- Mature B-cells released from bone marrow
- receptor interacts directly with pathogen
- affinity maturation
Antibody subclasses
IgM, IgG, IgE, IgA, IgD
why do we have booster vaccinations?
the secondary response to antigen is faster, greater and of increased duration
what are the effector cells of the adaptive immune response?
t lymphocytes
Tc cells : defend against infected cells, cancer cells and transplanted cells
B lymphocytes: secrete antibodies, present antigen to activate T cells
how do T cells develop?
- Developing T cells undergo two selection processes, positive then negative selection
positive: cells that don’t recognise self MHC
negative: cells that recognise self too strongly - mature cells become either Tc cells or Th cells
how do T cells get activated?
By recognition of antigen presented on MHC molecules
CTL activated by presented antigen from infected cell
TH cell activated by antigen
presented by Antigen Presenting Cell
