Hypersensitivity Of The Lungs Flashcards
Overview of innate immunity:
Non specific 1st line of defence Immediate response Phagocytes, NK cells, mast cells, baso and eosinophils E.g sputum and mucus
Overview of adaptive immunity:
Often second line of defence
Delayed often over 4 days
B and T lymphocytes
Pus, swelling etc
What is an antibody, produced by, job, types?
Protein produced by plasma cells, in response to an antigen.
Neutralises and eliminates pathogens.
IgG, IgA, IgM, IgE, IgD
What are all the types of antibodies and there function?
IgM - circulating tetramers mad at the beginning of infection
G - monomer highly specific antibodies targeting epitopes
A - expressed in mucosal tissue - protects neonatal gut
E - develop in response to parasitic threats
D - unknown function
What is the Gell and Coombs classification?
System that divides hypersensitivity into 4 categories
What is type 1 hypersensitivity?
Antigens interact with IgE antibodies bound to mast cells.
The mast cells release granules and powerful chemical mediators such as histamine and cytokines into the environment
This causes the characteristics/symptoms of the allergy
What is anaphylaxis?
Anaphylaxis is a systemic response to an antigen, leading to bronchoconstriction and vasodilation. This decline in oxygen transportation and can lead to anaphylactic shock and possibly death. It is usually treated with adrenaline, to dilate the bronchioles and constrict the blood vessels, antihistamines, to reduce the inflammatory effects of histamine, and corticosteroids, to reduce systemic inflammation.
Due to type 1 hypersensitivity
What is type 2 hypersensitivity?
Type 2 hypersensitivity reactions are mediated by antibodies targeting antigens on cell surfaces. When cell surface antigens are presented to T cells, an immune response is started, targeting the cells to which the antigens are attached.
Antibodies binding to cells can activate the complement system, leading to degranulation of neutrophils
The destruction of host cells in this way can lead to tissue-specific damage. Type 2 hypersensitivity reactions may occur in response to host cells (i.e. autoimmune) or to non-self cells, as occurs in blood transfusion reactions.
Type II hypersensitivity - mediators, timing and example?
Cytotoxic antibodies bound to cell antigen
Hours to days
Can happen during transfusions
What is type III hypersensitivity?
On exposure to the allergen antigen-immunoglobulin complexes are formed
These are deposited in tissues and cause local activation of complement and neutrophil attraction.
Typical takes 7-21 days
Example hypersensitivity pneumonitis
What is hypersensitivity pneumonitis?
Hypersensitivity pneumonitis is a rare immune system disorder that affects the lungs. It occurs in some people after they breathe in certain substances they encounter in the environment.
Farmers lung - mouldy hay
Pigeon fanciers lung - pigeons droppings or feathers
Etc
What is type IV hypersensitivity?
Type 4 hypersensitivity reactions are mediated by antigen-specific activated T-cells. When the antigen enters the body, it is processed by antigen-presenting cells and presented together with the MHC II to a Th1 cell.
If the T-helper cell has already been primed to that specific antigen, it will become activated and release chemokines to recruit macrophages and cytokines such as interferon-γ to activate them.
Activated macrophages release pro-inflammatory factors, leading to local swelling, oedema, warmth, and redness.
This reaction is also known as delayed-type hypersensitivity due to its characteristic longer time period to appear following antigen exposure. The reaction takes longer than all other types because of the length of time required to recruit cells to the site of exposure – around 24 to 72 hours.
Mediator, timing and example of type IV sensitivity?
T cells
Days to weeks or months
Tuberculosis
Note drugs can also often cause hypersensitivity but do not fall into the Gell and Coombs classification
Common example - ACE inhibitors
Check point inhibitors
What are check point inhibitors?
T cell recognises the antigen on a
cancerous cell
However PD-L1 block its destruction.
A check point inhibitor will block that meaning the cancer cell is destroyed.
However, it can also lead to other cells being destroyed - Diabetes, thyroid disease, pneumonitis etc
