Immunology

Question 1

SCID

1. Presentation of SCID
2. Cause of SCID
3. Cause of Omenn syndrome
4. Features of Omenn syndrome
5. Management of SCID

Answer 1

1. persistent diarrhoea, failure to thrive, opportunistic infections, unwell after live vaccinations, Omenn syndrome
2. Mutations in the common gamma chain on the X-chromosome that codes for interleukin receptors on T and B cells (X-linked). Also JAC3 mutations, mutations leading to adenosine deaminase deficiency
3. Mutation in RAG 1 or RAG 2 - autosomal recessive
4. erythroderma, alopecia, lymphadenopathy, hepatosplenomegaly, diarrhoea
5. Treating infections, Ig therapy, isolation, avoid live vaccines, HSCT

Question 2

Allergy

1. What is a type 1 hypersensitivity reaction?
2. Type 2?
3. Type 3?
4. Type 4?
5. Investigations
6. What is patch testing useful for?

Answer 2

1. IgE mediated -> mast cells and basophils release histamine and other cytokines
2. IgM and IgG antibodies react to an allergen and activate the complement system
3. Immune complexes accumulate and cause damage to local tissues
4. Cell-mediated, caused by T lymphocytes
5. SPT, RAST, food challenge
6. Contact dermatitis

Question 3

Anaphylaxis

1. Presentation
2. Management of anaphylaxis- generally
3. Medications used
4. How is anaphylaxis confirmed?

Answer 3

1. Urticaria, itching, angio-oedema, abdo pain, SOB, wheeze, swelling of larynx, tachycardia, collapse
2. ABCDE - secure airway, O2 if needed, salbutamol, IV bolus, lie flat.
3. IM adrenaline, chlorphenamine, IV hydrocortisone
4. Mast cell tryptase within 6 hours of event

Question 4

B Cell and Immunoglobulin Disorders

1. What is the most common immunoglobulin deficiency?
2. Presentation of IgA deficiency
3. Findings in CVID
4. Presentation of CVID
5. Management of CVID
6. Findings in XLA

Answer 4

1. Selective IgA deficiency
2. Often asymptomatic, recurrent mucous membrane infections
3. Low IgA and IgG, +/- deficiency in IgM
4. Recurrent respiratory tract infections, more prone to immune disorders such as RA and cancers such as NHL
5. Ig infusions, treating infections
6. Deficiency in all classes of immunoglobulins

Question 5

T Cell Disorders

1. What is diGeorge syndrome and what does it lead to?
2. Features of diGeorge (CATCH-22)

Answer 5

1. microdeletion in a portion of chromosome 22 that leads to a developmental defect in the third pharyngeal pouch and third branchial cleft -> incomplete development of thymus gland -> inability to create functional T cells
2. congenital heart disease, abnormal facies, thymus gland incompletely developed, cleft palate, hypoparathyroidism, 22nd chromosome