Immunology

Question 1

Cells of the immune system: granulocytes

Answer 1

BEN

• Basophils- stain blue
• Eosinophils- stain pink
• Neutrophils

Question 2

Cells of the immune system= antigen presenting cells

Answer 2

• Dendritic cells
• Monocytes- only found in the blood
• Macrophages- stays in the tissue, does not circulate in the blood
• B cells

Question 3

Cells of the immune system= lymphocytes

Answer 3

25% of total WCC in peripheral blood

CD34+ HSCT in bone marrow

IL2 = T, B + NK growth factors

IL7 + IL15 = T + NK development

• T cells (adaptive immune system)
• B cells (adaptive immune system)
• NK cells (innate immune system)

Question 4

Cells of the immune system = phagocytes

Answer 4

• Neutrophils, Monocytes, Macrophages
• Receptors
  
  • Fc= Ig
  • C3b= complement

Question 5

Function of dendritic cells

Answer 5

• ONLY antigen presenting cell that activates NAIVE T cells + initiates an immune response
• Critically important in vaccination
• Short lifespan = 3 days
• Single dendritic cell can present an antigen to several T cells

Question 6

Immunodeficiency conditions resulting in: recurrent sinopulmoonary infection

Answer 6

• Antibody production defects
  
  • CVID
  • X linked agammaglobulinaemia (XLA)
  • Transient hypogammaglobulinaemia of infancy
• Complement protein deficiencies

Question 7

Immunodeficiency conditions resulting in: broad infectious susceptibility + FTT

Answer 7

• SCID
• Wiskott Alrich
• DiGeorge
• Ataxia telangiectasia

Question 8

What is the cause?

Answer 8

XLA: x-linked agammaglobulinaemia

Absent B cells + hypogammaglobulinaemia

Question 9

CD3

Answer 9

T cell marker

Question 10

CD19 + CD20

Answer 10

B cell marker

Question 11

CD56

Answer 11

NK cell marker

Question 12

CD4

Answer 12

Helper T cell marker

Question 13

CD8

Answer 13

Cytotoxic T cell marker

Question 15

Disorders of humoral immunity (B cell differentiation + antibody production)

• Onset
• Pattern of infection
• Other features

Answer 15

Question 16

X linked (Bruton’s) agammaglobulinaemia

• KEY features
• Gene + protein implicated
• Clinical manifestations
• Investigations
• Management

Answer 16

Hypogammaglobulinaemia, NO circulating B cells, absent tonsils/lymph nodes

• Gene + protein implicated
  
  • Xq22- XLA gene
  • Bruton tyrosine kinase deficiency = pre B cell arrest
  • Males 1:100 000- 1:200 000
• Clinical manifestations
  
  • Well until ~ 6 months of age (maternal IgG antibodies protective until then)
  • Lymphoid hypoplasia
  • Recurrent infections with extracellular organisms (strep pneumonia, Haemophilus)
  • Viral infections usually handled except hepatitis + enterovirus
  • Paralysis with poliovirus
  • Chronic fungal infections
  • Types of infections: sinusitis, OM, pneumonia, sepsis, meningitis
  • Associated with rheumatoid arthritis, sarcoid
• Investigations
  
  • Neutropenia at HEIGHT of infection
  • Peripheral blood B lymphocytes <1%
  • High T cell percentage, normal T cell subset ratios
  • Normal T cell function + thymus
  • LOW or absent immunoglobulins
  • Antibodies to vaccines absent
  • Intestinal biopsy= absence of plasma cells
  • Prenatal testing can be performed
• Management
  
  • Lifelong IVIG (does NOT correct IgA deficieincy or prevent enterovirus)
  • Antibiotics

Question 17

Answer 17

D) Specific antibody responses to vaccine antigens should be assessed

Question 18

Criteria for common variable immunodeficiency (CVID)

Answer 18

Question 19

T cell dependent + independent vaccines

Answer 19

• T cell dependent: isotype switched, high affinity, long lived plasma cells (IgA, IgG, IgE)
  
  • Protein vaccinations (Diptheria, tetanus, HiB, PCV)
• T cell independent: mainly IgM, short lived plasma cells
  
  • Polysaccharide vaccinations (Pneumovax 23)

Question 20

What is the diagnosis?

Answer 20

Severe combined immunodeficiency

• PJP + FTT + thrush
• Anaemia + lymphopenia
• Hypogammaglobulinaemia
• Low CD3 (T cell marker) + CD56 (NK cell marker)
• PHA (T cell mitogen response) = low

Question 21

Answer 21

X-linked Hyper IgM = T cell defect

Question 22

Answer 22

Chronic granulomatous disease

Question 23

What is recognised by the innate immune system?

Answer 23

PAMPS + DAMPS

Question 24

CD28

Answer 24

Co stimulatory molecule on T cells which binds to B7 on antigen presenting cells and causes proliferation + differentiation. If B7 on the APC not present then it will not cause activation of the T cell.

Question 25

CTLA4

Answer 25

* Inhibitor of T cell activation. Binds to B7 on APC and inactivates it. * HIGHER affinity to B7 than CD28