I6 Drivers of Inflammation and Immunodeficiency

Question 1

Learning Outcomes (for general perusal)

Answer 1

● Cytokines:-

proinflammatory

anti-viral

involved in haematopoiesis

involved chemotaxis

in suppression, tolerance and therapy

● Causes of primary and secondary Immunodeficiency

Question 2

What is homeostasis?

Why is this important?

Answer 2

The property of a system, especially a living organism, to regulate its internal environment so as to maintain a stable, constant condition.

Ability of the immune system to self-reguate is critical. Inflammation underpins most chronic diseases.

• Hypersensitivity (viral infection)
• Chronic Inflammation (bacterial infection)
• Immunodeficiency (recovery)
• Immunosuppression (tissue repair)

Question 3

What are the signs of inflammation?

What are the main drivers of inflammation?

Answer 3

• Rubor
• Tumor
• Calor
• Dolor
• Functio Laesa

Cytokines

Question 4

1. What are Cytokines?
2. Why are many cytokines known as interleukins?
3. What do they play an important role in linking?

Answer 4

1. Cytokines are potent chemical messengers produced by cells of the immune system. Small peptides that are usually secreted. (Lymphokines and monokines collectively called cytokines)
2. Cytokines act as a messenger between leukocytes
3. linking innate and adaptive immunity

Question 5

Cytokines

1. Give some properties
2. Generally, how do they act?

Answer 5

1. Low molecular weight proteins. Their production is carefully regulated
2. Bind to receptor on the cell which produced it or another cell

Receptor binding triggers a signal

Signal results in altered pattern of gene expression

Question 7

Cytokines

They can act in three different ways.

Name these ways, and outline how the cytokines act.

Answer 7

1. Autocrine - Cytokine binds to receptor on cell that secreted it
2. Paracrine - Cytokine binds to receptors on nearby cells
3. Endocrine - Cytokine binds cells in distant parts of the body

Question 8

Cytokines

1. How do they signal?

Answer 8

1. Through cytokine receptors, TI and TII cytokines (JAK family tyrosine kinases, phosphorylation of R. STAT phosphorylation, STAT dimerisation, into nucleus and acts upon specific gene transcription)

Question 9

1. How are cytokines classified?
2. How many interleukins have been identified to date?

Answer 9

1. Into four families based on their structure
   
   1. Haematopoietin Family (eg: IL-2 and IL-4)
   2. Interferon family (IFNs)
   3. Tumour necrosis factor family (eg:TNF-α)
   4. Chemokine Family (eg: CCL-2)
2. 35 Interleukins

Question 10

How do Cytokines regulate hematopoiesis?

Answer 10

• Common lymphoid progenitor will give rise to NK cells and T and B lymphocytes under the action of IL-7
• Common myeloid progenitor will give rise to Erythroid Progenitor, Megakaryocyte, Basophil progenitor, Eosinophil projenitor and Granulocyte-monocyte projenitor under the actions of IL-3, GM-CSF, IL-6
• Eosinophil from eosinophil projenitor by IL-5
• Neutrophils (by GM-CSF) and Monocytes (by M-CSF) from granulocyte-monocyte projenitor

Question 11

What are cytokines important in linking?

Answer 11

The innate and adaptive immune response. Secreted by Th cells

• Guides clonal expansion of Th cells and Tc cells
• Activates resting B cells into Active B cells then into Plasma Cells (IL-6)
• Guides differentiation of mast cells, Eosinophils, NK cells

Question 12

Role of Cytokines in Immune Response

1. What is their primary function in the immune response?
2. Give some speficic cell interactions that they guide

Answer 12

1. Linking the innate and the immune response (there is also an initial pro-inflammatory response)

2.

• Interaction between T cell and APC
• DC instruction to T cell
• T cell polarisation - Th1, Th2, Th17
• Anti-viral response

Question 13

Interleukin-2

1. ​When is it produced?
2. How does it act?
3. Outline its specific actions further

Answer 13

1. following T cell activation by antigen presenting cells.
2. acts in an autocrine loop to induce T cell proliferation
3. The major autocrine growth factor for T cells.

IL-2 (and IL-15) stimulates NK cell cytolytic function.

Acts on B cells as a growth factor. Induces the death of activated T cells

IL-2 receptor has 3 chains IL-2Rαβγ. The α chain is the cytokine specific chain and the γ chain is shared by a number of cytokine receptors

Question 14

Interleukin-4

1. What is it?
2. What does it do?
3. What is it produced by?
4. What is it required for the production of?
5. What does it induce?
6. How does it interact with Mast cells?

Answer 14

1. a Th2 derived cytokine
2. stimulates B cell proliferation. Exogenous IL-4 drives Th2 differentiation
3. Activated Thelper2 cells
4. gG1 and IgE
5. Thelper2 cell differentiation
6. It is a growth factor for mast cells

Question 15

Interleukin-17

1. What is it produced by?
2. What does it do?
3. What conditions is it associated with?
4. What is it?

Answer 15

1. Activated Thelper17 cells
2. Induces neutrophil maturation and activation
3. autoimmune pathologies (rheumatoid arthritis, lupus, psoriasis) drives bone resorption in arthritis. a major role in many infectious diseases
4. major pro-inflammatory cytokine

Question 16

Inhibitory Cytokines

1. What are the inhibitory Cytokines?
2. Outline what each does and where they are produced

Answer 16

1. TGF-B, IL-10

2.

TGF-B- generally suppresses lymphocyte function, produced by many cells of the immune system

• Suppresses the activation of macrophages
• Inhibits growth of many cell types especially lymphocytes
• Enhances wound repair

IL-10 - generally suppresses the immune system, produced by activated T Helper 2 cells and T regs

• Is required for suppression of macrophages, T cells, NK cells
• Inhibits TNF, IL-1, IL-12 and chemokine production The absence of IL-10 causes IBD

Question 17

Outline T Cell subsets and defence against pathogens

Answer 17

T_H2 - secretes IL-4 - defence against parasitic worms. Allergy, asthma.

T_H1 - secretes IF-gamma - defence against intracellular pathogens

T_H17 - secretes IL-17 - defence against extracellular bacteria, autoimmunity, cancer

T_reg - secretes TGF-B1 - immunosuppression

Question 18

Cytokines produced by Macrophages in response to bacterial challenge

Activated macrophages secrete a range of cytokines

What are these cytokines? What do they do?

Answer 18

• IL-1 - Activates vascular endothelium, lymphocytes, local tissue destruction, increases access of effector cells: fever IL-6
• TNH-a - Activates vascular endothelium, increases vascular permeability (increased entry of IgG, complement and cells to tissues and increased fluid drainage to lymph nodes): fever, mobilisation of metabolites, shock
• IL-6 - Lymphocytes activation, increased, increased antibody production: fever, induces acute-phase protein production
• IL-8 - Chemotactic factor results in neutrophils, basophils and T cells to site of infection
• IL-12 - activates NK cells, induces differentiation of CD4 cells to Th cells

Question 19

Outline the anti-viral effects of interferon a/b

Answer 19

• Induce resistance to viral replication in all cells
• Increase MHC class 1 expression and antigen presentation in all cells
• Activate NK cells to kill virus infected cells

Question 20

Tumour Necrosis Factor-α (TNF-α)

1. Generally, what does it do?
2. What is it derived from?
3. What does it induce?
4. What can it induce long-term?
5. What does it act on the hypothalamus to produce?

Answer 20

1. Principle mediator of the anti-bacterial response
2. macrophages and T cells
3. Induces neutrophil activation (inflammation)

Activates endothelial cells (inflammation)

4. Long-term it can induce cachexia (muscle and fat wasting)
5. Fever

Question 21

Chemokines

1. ​What are these?
2. What do they do?

Answer 21

1. Chemotactic cytokines
2. Recruit leukocytes to sites of infection

Regulate traffic through peripheral lymphoid tissues

Organ development (morphogenesis) Lymph node organization
 Cell activation

structurally homologous 8-12 kDa

50 or more already described

Question 22

What are the main chemokine families?

Answer 22

C (XCL1,2)

CC (CCL2,3,4)

CXC (CXCL1,8,9,10,12)

CX₃C (CX₃CL1)

Question 23

Outline chemotaxis

Answer 23

Attracted leukocyte (macrophage) has Rs on surface, moves towards inflammatory site along the chemotactic gradient

Question 24

Outline Chemokine signalling?

Answer 24

Transmembrane chemokine receptor coupled to G protein.

Cellular cascade results in

• Actin polymerisation
• Adhesion
• Cytoskeletal rearrangement

These all contribute to chemotaxis

• Differentiation, proliferation

Question 25

**Cytokine Dysregulation** Outline cytokine dysregulation in 1. Asthma 2. Allergy 3. Autoimmunity

Answer 25

1. Dysregulation of Th1/Th2 balance. **Th2 cytokines overproduction** 2. Chronic inflammatory response: **dysregulation of Th17 cells**

Question 26

**Other cytokine related diseases** 1. Bacterial septic shock 1. What are the symptoms? 2. What is the pathological process? 2. Lymphoid and myeloid cancer 1. Why does this come about? 3. Chagas’ disease 1. What is this?

Answer 26

1. Bacterial septic shock 1. Blood pressure drops, clots form, hypoglycemia ensues, patient dies 2. LPS(lipopolysaccharide) triggers results in TNF release TNF induces IL-1 which induces IL-6 and IL-8 2. Some cancer cells secrete cytokines 3. Trypanosoma cruzii infection results in severe immune suppression ◦Depression of IL-2 receptor production

Question 27

**Cytokine Receptors in Disease** 1. What do mutations in R shared by IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21 cause? 2. What can EPO ( Erythoropoietin) receptor mutations cause? 3. What does TNF receptor mutations cause? 4. What is consitutive activation of cytokine signalling pathways associated with?

Answer 27

1. **X**-**SCID** (X- linked severe combined immunodeficiency) 2. benign **erythrocytosis** 3. tumour necrosis factor receptor associated periodic syndrome (**TRAPS**) 4. many leukaemias.

Question 28

**Cytokines in Therapy** 1. What has been used to treat cancer? 2. What is the main therapy in viral hepatitis? 3. What is the main therapy for MS? 4. What is IFN-g used to treat? 5. What is IL-10 under investigation for treating? 6. What is EPO used for? 7. What can be used following bone marrow transplantation? 8. What is used to treat rheumatoid arthiritis? 9. What is under investigation to treat IBD?

Answer 28

1. IL-2 2. IFN- a is the main therapy viral hepatitis also Leukemia 3. IFN- b is the main therapy for Multiple Sclerosis 4. IFN-g used to treat chronic granulomatous disease 5. autoimmune diseases 6. to treat patients prior to transplantation as it stimulates erythrocyte proliferation; has neuroprotective effects (stroke). 7. G-CSF 8. Antibodies to TNF (anti-TNF) 9. Antibodies to IL-12 (anti-IL-12)

Question 29

**Primary Immunodeficiency Diseases** 1. What are the clinical features? 2. What are examples? 3. What is the main characterisitic? 1. What are the adaptive immune defects? 2. What are the innate immune defects?

Answer 29

1. Clinical feature variable. Recurrent and often overwhelming infection in very young children 2. Allergy, autoimmunity, cancer, lymphocyte abnormal proliferation 3. Inherited mutations 1. T cells, B cells, antibodies 2. Complement components Phagocytes TLRs signalling

Question 30

**Primary Immunodeficiency Diseases** *_T-Lymphocyte Deficiencies_* What can cause these?

Answer 30

* Deficiency of Signalling Molecules * Jak3, Lck, Zap70 , CD45 * 􏰁 RAG-1 & RAG-2 deficiency * combination activating genes * 􏰁 Ataxia Telangiectasia * 􏰁 MHC Class I & Class II deficiency * (Bare lymphocyte syndrome) * 􏰁 X-linked lymphoproliferative disease

Question 31

**Primary Immunodeficiency Diseases** *_T-Lymphocyte Deficiencies_* 1. What do defects in T-cell development result in? 2. What is DiGeorge Syndrome? 3. What gives rise to Deficiency of Cytokine Receptor chains? 4. What is Wiskott-Aldrich Syndrome (WAS)? 5. Give examples of a metabolic defect

Answer 31

1. **severe combined immunodeficiencies ( SCID)** 2. Intra-uterine damage to 3rd and 4th Pharangeal pouches 3. ◦ X-linked SCID: mutation in the gene IL2RG on the X chromosome ◦ common gamma chain ◦ IL-7 receptor α & IL-2 receptor α 4. membrane defects of T cells and platelets 5. -Adenosine Deaminase Deficiency - Purine Nucleoside Phosphorylase Deficiency

Question 32

**Secondary Immunodeficiency Diseases** 1. What are these a result of? 2. Give an example

Answer 32

1. A consequence of other diseases Environmental factors An adverse consequence of medical interventions such as chemotherapy 2. Acquired immune deficiency disease (AIDS)

Question 33

**Acquired immune deficiency disease (AIDS)** 1. What is it a result of? 2. What are the actions of this virus? 3. What does it leave the sufferer prone to?

Answer 33

1. Human immunodeficiency virus (HIV) 2. HIV infects CD4 T cells, macrophages and dendritic cells.􏰁 A massive reduction in the number of CD4 T cells. 3. Severe infections by pathogens