Immuno: Immune modulating therapies 1

Question 1

List some approahces to boosting the immune system.

Answer 1

• Vaccination
• Replacement of missing components (e.g. replacing immune cells)
• Blocking immune checkpoints
• Cytokine therapy

Question 2

Describe the variety of antigen receptors found in the adaptive immune system.

Answer 2

• Contains a wide variety of antigen receptors
• Not entirely genetically encoded as genes are rearranged and recombined
• This has the potential to generate autoreactive cells but these are removed
• The adaptive immune system has exquisite specificity

Question 3

What happens when cells of the adaptive immune system engage with an antigen that it recognises?

Answer 3

Undergoes massive clonal expansion

Question 4

What are the two ways in which B cells can undergo clonal expansion once activated?

Answer 4

• They can differentiate into T-cell independent IgM plasma cells
• They can undergo a germinal centre reaction (with help from T helper cells) and become IgG memory and plasma cells

Question 5

Which type of T cell undergoes a more pronounced proliferation following activation?

Answer 5

CD8 > CD4

Question 6

List three types of antigen-presenting cell.

Answer 6

• Dendritic cells
• Macrophages
• B lymphocytes

Question 7

What are some important characteristics of memory T cells?

Answer 7

• Longevity - memory T cells persist for a long time in the absence of antigen due to low level proliferation in response to cytokines
• Different pattern of cell surface proteins involved in chemotaxis cell adhesion - allows memory cells to rapidly access non-lymphoid tissues
• Rapid, robust response to subsequenct antigen exposure (lower threshold for activation of naïve T cells)

NOTE: memory B cells have similar characteristics and are able to produce rapid and robust responses

Question 8

What are the aims of vaccines?

Answer 8

• Generate protective, long-lasting immunity
• No adverse reactions
• Single shot
• Easy storage

Question 9

Which cell surface receptor is used in the influenza vaccine?

Answer 9

Haemagglutinin (HA) - this is a receptor-binding and membrane fusion glycoprotein

Question 10

Describe how haemagglutinin inhibition assays work.

Answer 10

• If you put normal red blood cells in a petri dish, they will clump at the bottom forming a red spot
• If you add influenza virus, the HA makes red cells stick together and causes a diffuse coloration across the well
• If you add the serum of someone who has a lot of antibodies against HA, it will inhibit the haemagglutination effects of HA so the red cells remain as a discrete red spot
• The higher the dilution of serum at which the red cells remain as a little dot, the more antibodies are present in the serum

NOTE: sialic acid receptors on RBCs bind to HA leading to haemagglutination

Question 11

How long does protection from the influenza vaccine last?

Answer 11

Starts 7 days after the vaccine and protection lasts for 6 months.

Question 12

What agent is used in the BCG vaccine?

Answer 12

Attenuated strain of Mycobacterium bovis.

Question 13

Describe the protection that is achieved by using the BCG.

Answer 13

• Some protection against primary infection
• Mainly protects against progression to active TB

NOTE: T cell response is important in protection

NOTE: protection lasts for 10-15 years

Question 14

What is the Mantoux test?

Answer 14

• A small amount of liquid tuberculin (PPD) is injected intradermally
• The area of injection is examined 48-72 hours after the injection
• A reaction would appear as a wheel around the injection site (this is suggestive of latent TB, active TB or previous BCG)

Question 15

What is a live attenuated virus vaccine? List some examples.

Answer 15

The organism is alive but modified to limit its pathogenesis.

Examples: MMR, typhoid, BCG, yellow fever, polio (Sabin)

Question 16

List some advantages and disadvantages of live attenuated virus vaccines.

Answer 16

• Advantages: establishes infections, raised broad immune response against multiple antigens, activates all phases of the immune system, often confer life-long immunity after one dose
• Disadvantages: storage problems, possible reversion to virulence, spread to contacts, cannot be used in immunocompromised patients

Question 17

List some examples of the following types of vaccine:

1. Toxoids
2. Component/Subunit

Answer 17

1. Toxoids
   
   • Diphtheria
   • Tetanus
2. Component/Subunit
   
   • Hep B (HBsAg)
   • HPV (capsid)
   • Influenza (HA)

Question 18

What are the advantages and disadvantages of inactivated/component vaccines?

Answer 18

• Advantages - no mutation or reversion, can be used in immunodeficient patients, easier storage, lower cost
• Disadvantages - often do not follow normal route of infection, poor immunogenicity, may need multiple injections, may require conjugates/adjuvants

Question 19

Describe how conjugate vaccines work.

Answer 19

• Polysaccharide and protein carrier
• Polysaccharide induces a T-cell independent B cell response (transient)
• Addition of the protein carrier promoted T cell immunity which enhances B cell/antibody responses

Question 20

List some examples of conjugate vaccines.

Answer 20

• Haemophilus influenzae type B
• Meningococcus
• Pneumococcus

Question 21

Describe how adjuvants work.

Answer 21

• Increases the immune response without altering its specificity
• They mimic the action of PAMPs on TLF and other PRRs

Question 22

List some examples of adjuvants.

Answer 22

• Aluminium salts (MOST COMMON)
• Lipids (monophosphoryl lipid A)

NOTE: the mechanism of action of aluminium salts is not fully understood but it may allow antigens to be released slowly over time, may induce a mild inflammatory reaction or may activate Gr1 + IL4 + eosinophils

Question 23

List some example of experimental vaccine adjuvants.

Answer 23

• ISCOMs - immune-stimulating complexes (enhances cell-mediated immunity)
• CpG - cytosine-phosphate-guanosine motif that can bind via PRR to induce an immune response
• DNA vaccines - plasmid containing a gene of choice (e.g. from a pathogen) is inserted into a muscle cell which will then express the antigen. This stimulates T cells responses (WARNING: this can lead to autoimmunity)

Question 24

What are dendritic cell vaccines?

Answer 24

• Used against tumours
• You collect some dendritic cells from the patient and load them with the antigen from the tumour to try and boost the immune response against tumour antigens

Question 25

What are the main indications for haematopoietic stem cell transplantation?

Answer 25

* Life-threatening immunodeficiency (SCID) * Haematological malignancy

Question 26

What is human normal immunoglobulin?

Answer 26

* Immunoglobulin prepared from thousands of pooled donors * Contains pre-formed IgG * Administered IV or SC

Question 27

List some indications for IVIG

Answer 27

* Primary antibody defect * X-linked agammaglobulinaemia * X-linked hyper IgM syndrome * Common variable immunodeficiency * Secondary antibody defect * CLL * Multiple myeloma * After bone marrow transplantation

Question 28

When might specific immunoglobulin be given?

Answer 28

Passive immunity as post-exposure prophylaxis (e.g. Hep B, tetanus, rabies, VZIG)

Question 29

List four types of T cell adaptive cell transfer.

Answer 29

* Virus-specific T cells * Tumour infiltrating T cells (TIL) * T cell receptor T cells (TCR) * Chimeric antigen receptor T cells (CAR T Cell Therapy)

Question 30

Using an example, describe how virus-specific T cells are used.

Answer 30

* Used for EBV in patients who are immunosuppressed to prevent the development of lymphoproliferative disease * Blood is taken from the patient or from a donor * Peripheral blood mononuclear cells are isolated and stimulated with EBV peptides * This creates and expansion of EBV-specific T cells which are then reinfused into the patient NOTE: tumour infiltration T cell therapy follows the same principle but uses tumour antigens

Question 31

Describe how TCR and CAR T cell therapy works.

Answer 31

* T cells are taken from the patient and vectors are used to insert gene fragents that encode receptors * In TCR therapy, the gene will encode a specific TCR (e.g. against tumour antigen) * In CAR therapy, the receptors are chimeric (containing both B and T cell components)

Question 32

Describe a use of CAR T cell therapy.

Answer 32

* Used to target CD19 (present on B cells) * Receptors on the CAR cell have an immunoglobulin variable domain and is joined to a TCR * This means that it recognises CD19 through an immunoglobulin domain but signals through the TCR pathway NOTE: this is used in ALL and NHL

Question 33

What is ipilimumab and how does it work?

Answer 33

* CTLA4 and CD28 are both expressed by T cells and they recognise antigens (CD80 and CD86) on APCs * Signalling through CD28 results in a stimulatory response * Signalling through CTLA4 results in an inhibitory response * Ipilimumab is a monoclonal antibody that blocks CTLA4 thereby removing this inhibitory response * It is used in advance melanoma

Question 34

Explain the use of antibodies against PD-1 in treating cancer.

Answer 34

* PD-1 and PD-2 ligands are present on APCs and interact via PD-1 receptors on T cells to cause an inhibitory response * They can also be expressed by some tumour cells * Pembrolizumab and nivolumab are antibodies that are specific to PD-1, thereby blocking this effect * This is also used in advanced melanoma

Question 35

List some examples of the therapeutic use of recombinant cytokines.

Answer 35

* Interferon alpha - used as an adjunct in the treatment of Hep B, Hep C, Kaposi sarcoma, CML and multiple myeloma * Interferon beta - Behcet's disease, relapsing MS * Interferon gamma - chronic granulomatous disease