Immunology

Question 1

Allergy

What is the difference between Allergy and Atropy

*LOB: Recognise the importance of a clinical history in the diagnosis of allergy and atopy

Answer 1

Allergy refers to a clinical condition where an IgE-mediated Type I hypersensitivity reactionoccurs upon exposure to a specific allergen. This results in symptoms like hay fever, asthma, hives, or anaphylaxis.

Atropyrefers to the** genetic predisposition** to produce specific IgE antibodies when exposed to common environmental allergens

Question 2

Allergy

How is allergy diagnosed?

*LOB: Recognise the importance of a clinical history in the diagnosis of allergy and atopy

Answer 2

A detailed clinical history is crucial in planning allergy tests
* suspected triggers
* the time course of allergic reactions
* seasonality of symptoms
* where symptoms worsen (indoors/outdoors).

Question 3

Allergy

Pathophysiology of Allergu

*LOB: Understand the basic pathophysiology of an allergy mediated response

Answer 3

Allergies are primarily IgE-mediated Type I hypersensitivity reactions. Mast cells, which are widely distributed in tissues, play a central role by degranulating and releasing mediators like histamine when specific IgE antibodies attached to their surface are cross-linked by allergens. This causes symptoms such as vasodilation, pruritus, and bronchospasm​

Question 4

Allergy

Investigate Allergy

*LOB: Recognise the importance of a clinical history in the diagnosis of allergy and atopy

Answer 4

Skin Prick Testing (SPT) and Specific IgE blood tests are the primary methods for allergy testing. SPT is performed in vivo on the patient’s skin, while blood tests measure allergen-specific IgE in serum. Other tests include serum total IgE, which indicates atopy but is not used for screening, and the basophil activation test (BAT), which measures basophil activation by allergens​

Question 5

Allergy

limitations in the interpretation of allergy testing:

*LOB:Explain the limitations in interpretation of allergy testing

Answer 5

Positive results from skin or blood tests only confirm IgE sensitization, which does not necessarily indicate clinical allergy. Some individuals may have positive results without exhibiting allergic symptoms, and false positives can occur, especially in conditions like eczema

Question 6

Allergy

Serum Tryptase

*LOB:Describe the utility of serum tryptase measurement

Answer 6

serum tryptase is a useful marker of mast cell degranulation and is typically elevated after an anaphylactic reaction. It should be measured within 15 minutes to 3 hours after the onset of symptoms, with a second sample taken 3–6 hours post-reaction. Persistent elevations in baseline tryptase levels may indicate conditions like mastocytosis​

Question 7

Allergy

TERMINOLOGY DESCRIBING SOME COMMON REACTIONS TO FOOD

Answer 7

1. “True food allergy” - IgE mediated de-granulation of mast cells.
   Common food allergens: cow’s milk protein, egg, peanuts, tree nuts, fish, prawns

NB: ‘Oral allergy syndrome’ is due to cross reacting ‘pan-allergens’ which are found in various members of the plant family (fruits, vegetables, nuts etc). They are heat labile and destroyed by digestion, hence symptoms are usually limited to the oral cavity.

2. “False food allergy”- direct stimulation of mast cells or histamine ingestion
   Scombroid fish poisoning (scombrotoxicosis) – Histamine is released by bacterial action (spoilage) on scombroid fish (e.g tuna). Symptoms that mimic an allergic reaction occur when the spoiled fish containing histamine is consumed.
3. “Food intolerance”- adverse reaction to food, with no histamine related symptoms
   e.g Lactose intolerance, gluten sensitivity
4. “Food sensitivity”-an ‘umbrella’ term for all of the above
5. “Food aversion”- psychological

Question 8

Allergy

Management of Food Allergy

Answer 8