Lab8 Flashcards
Questions page 55, 61, not answered
How common are allergies?
Very common, they affect up to 25% of the population
What is type I hypersensitivity?
an allergic reaction
How is type I hypersensitivity provoked?
In response to exposure by ingetstion, inhalation, injection, or direct contact with specific allergen
What does this lead to?
An overproduction of IgE
What are some examples of Type I hypersensitivity?
Asthma, Dermatitis, Rhinitis, Allergic conjunctivitis and Urticaria
What is an important part of allergy treatment?
To avoid the antigen triggering the process (avoid the allergen)
How can the allergen be avoided?
There may be clues from a patient’s clinical history, however it is often not possible to identify the allergen solely from the history
What is the best test for type I hypersensitivity?
The skin prick test.
This is a very sensitive way of detecting the presence of IgE antibodies against a panel of candidate allergens
It is inexpensive and very safe
How does the skin prick test work?
Circulating IgE molecules are captured by Fc receptors expressed on mast cells underlying the skin
The allergen crosslinks the Fc receptor-bound IgE antibodies triggering mast cell degranulation which produces a wheal on the skin
Which antigens are the most important to be matched for blood transfusions?
The ABO antigens
What does it mean if someone is in blood group AB?
They have both antigens on their red blood cells.
What does it mean if someone is in group O?
They have neither A or B antigen present in blood cells
What is the second most important blood grou system for blood transfusions?
The Rhesus blood group system
Of the five main rhesus antigens which one is the most important and why?
RhsD because it is the most immunogenic
How many subgroups are there in the Rhesus group system?
2.
People may either be Positive or negative for the presence of the RhD antigen
What are all blood donations typed for?
ABO antigens and RhD, and for other antigens on the surface of red blood cells
What are analogous matching proceudres performed for?
Tissue transplants
Including
Corneal grafts in circumstances where a patient has previously rejected a corneal transplant
or where new blood vessels have grown into their damaged cornea. These blood vessels introduce immune cells into this normally avascular region of the eye that might later recognise the graft as foreign and attack it.
How are ABO blood groups determined by?
Haemagglutination - which is the agglutination of red blood cells
How is haemagglutination carried out?
Diluted blood is mixed with antibodies against antigens A or B or against RhD
If cells agglutinate due to the formation of a large red cell-immune complex, then the respective antigen is present on the cells.
Why are positive and negative controls included in the skin testing?
So that the intensity of the allergic reaction can be assessed
What are two ways in which allergies can be fatal?
- triggered by antigen
2.
Most antigens are composed of proteins. ABO blood group antigens are not. What are they made of?
Sugars
What is the difference between A, B and O antigens?
The difference between these antigens is found in the terminal sugar residue of the carbohydrate portion of the antigen
What can happen if someone receives a blood transfusion with the wrong blood group?
An immune response can be activated which causes a hemolytic reaction which could kill a lot of the person’s red blood cells.
