HD16 Allergic Diseases Flashcards
What are the allergic response symptoms that you may see that are sever and potentially lifethreatening?
2) What should you do after dealing with the crisis?
1) breathing difficulties, swelling and itching, urticaria/ hives, incontinance, diarrhoea, cramps
2) refer to appropriate specialists for further investigation
What is hypersensitivity?
Immune mediated antigen-specific reaction that are inappropriate or excessive and result in harm to the host.
What 2 ways can hypersensitivity be mediated?
Antibody mediated
T cell mediated
What 3 things can hypersensitivity be against?
Environmental agents
Self antigens
Infectious agents e.g. hep B, leprosy (tuberculoid reactions)
Whats the other name of a type 1 hypersensitivity?
immediate mediated (IgE)
Whats the other name of a type 2 hypersensitivity?
antibody mediated
Whats the other name of a type 3 hypersensitivity?
immune complex mediated
Whats the other name of a type 4 hypersensitivity?
T cell mediated (delayed)
Whats the other name of a T cell mediated hypersensitivity?
type 4
Whats the other name of a immune complex mediated hypersensitivity?
type 3
Whats the other name of a antibody mediated mediated hypersensitivity?
type 2
Whats the other name of a immediate mediated hypersensitivity?
type 1
What type of antibody is involved in type 1 hypersensitivity?
IgE
What antibodies are involved in type 2 hypersensitivity?
IgM , IgG
What antibodies are involved in type 3 hypersensitivity reactions?
2) Anything else involved?
1) IgM and IgG
2) extracellular matrix antigens
what is involved in type 4 hypersensitivities?
CD4 + T cells (delayed- type hypersentivity)
CD8+ CTLs (T cell mediated cytolysis)
Describe the mechanisms of tissue injury and disease through type 1 hypersensitivity?
mast cells and their mediators (vasoactive amines, lipid mediators and cytokines)
Describe the mechanisms of tissue injury and disease through type 2 hypersensitivity?
so the antibody binds to an intrinsic (self) or extrinsic (come from pencillin or virus) antigen on a host cell e.g. RBC=
1) opsonisation and phagocytosis of cells
2) complement and Fc receptor mediated recruitment and activation of leukocytes (neutrophils, macrophages)
3) abnormalities in cellular functions e.g. hormone receptor signalling
Describe the mechanisms of tissue injury and disease through type 3 hypersensitivity?
complement and Fc receptor mediated recruitment and activation of leukocytes
(this one is similiar to type 2, but misses out a few of the responses due to not involving extracellular matrix antigens)
Describe the mechanisms of tissue injury and disease through type 4hypersensitivity?
- CD4+ T cell= macrophage activation, cytokine-mediated inflammation
2, CD8+ CTLs = direct target cell killing, cytokine mediated inflammation
What is the hygiene hypothesis
Decreased infection
Increased immunisation
Leads to preferential switch from type 1 profile to type 2 profile
What is atopy?
Atopy refers to the genetic tendency to develop allergic diseases such as allergic rhinitis, asthma and atopic dermatitis (eczema)
In type 1 hypersensitivity. IgE mediated degranulation of mast cells and basophils.
What is released?
Release of histamine, heparin, lysosomal enzymes and proteases
What are the clinical consequences caused by increased cappillary permeability with hypersensitivity reactions?
Tissue oedema, urticaria, itching, rhinitis
Laryngeal oedema: (Airway obstruction,,
Respiratory distress
Stridor)
Fluid leakage from vascular space (Hypovolemic shock)
What are the clinical consequences caused by smooth muscle contraction with hypersensitivity reactions?
Bronchospasm: (Respiratory distress, cough)
GI tract spasm: (Nausea, vomiting & Cramps, diarrhoea)
Bladder spasm (Urinary urgency/incontinence)
What investigations are undertaken to diagnosis hypersensitivity to a particular antigen?
- skin prick tests
- blood tests (specific IgE)
- challenge tests (to overcome false positives and negative results: could be given oral/iv (double blind placebo controlled)
What is the definition of anaphylaxis?
Severe allergic reaction with 1 or both of:-
Breathing difficulties
hypotension
What do u if a patient is in anaphylaxis, (especially if skin changes are present)
oxygen
following anaphylaxis and treatment with oxygen, what would you do if this then occured:
Stridor, wheeze, respiratory distress or clinical signs of shock
Adrenaline 1:1000 2,3 solution; 0.5ml (0.5mg) intramuscular
patient has anaphylaxis, oxygen administered then , wheezing occurs then Adrenaline 1:1000 2,3 solution; 0.5ml (0.5mg) administered intramuscularly:
2) what do you do if this doesn’t help?
Repeat asministering adrenaline in 5 mins if no clinical improvement
2) Antihistamine (chlorpheniramine) 10-20mg IM or slow IV
For all severe or recurrent reactions and patients with asthma give ………..
For all severe or recurrent reactions and patients with asthma give hydrocortisone 100-500mg IM or slow IV
If clinical manifestations of shock do not respond to drug treatment give …..
1-2L of fluid IV4. Rapid infusion or one repeat dose may be necessary.
What are the 3 things used to treat type 1 reactions?
antihistamines e.g. Cetirizine
steroids e.g. Prednisolone, hydrocortisone
bronchodilators e.g. salbutamol
