L8 Regulating the immune responses: the role of cytokines and chemokines : the role of cytokines and chemokines Flashcards
How do cytokines act
- All cytokines act by ligating their receptor (often two subunits) and triggering a signalling cascade leading to activated transcription of specific genes
Cytokines in hematopoiesis
IL-, interleukin, SCF, stem cell factor; G-(GM)-CSF, granulocyte (granulocyte/macrophage) colony stimulating factor: EPO, erythropoietin; TPO, thrombopoietin
What are interferons
- Anti-viral mediators
- Products of virus-infected cells that interfere with viral replication
Examples of interferons
- IFN-alpha (made by lymphocytes)
- IFN-beta (made by fibroblasts)
- IFN-gamma (made by lymphocytes and NK cells)
Immune activators that are involved in mediating host defense
- Lymphocyte-activating cytokines (IL-1)
- T cell growth factors (IL-2, -7, -9, -15; they share a co-receptor)
- Macrophage-activating cytokines (IFN-gamma)
What are cytotoxins
- Identified as products of activated lymphocytes or macrophages that can kill tumour cells
eg. tumour necrosis factor; TNF, also known as TNF-alpha
Why wasn’t TNF used as an anticancer agent
- TNF was cloned and produced with the hope it would be an anticancer agent
- However, it turned out to te too toxic
- Same story for IL-1, as a lymphocyte activator tested in AIDS
Three main types of armed effector T cells
- Cytotoxic (killer) T cells (Peptide + MHC class I)
- Tn1 and Tn2 cells (peptide + MHC class II)
Effector molecules produced by cytotoxic (killer) T cells
- Cytotoxic effector molecules
Effector molecules produced by Tn1 cells
- Macrophage-activating effector molecules such as IFN-gamma and TNF-alpha
Effector molecules produced by Tn2 cells
- B-cell activating effector molecules such as IL-4,5,15,10 and TGF-beta
How do Th1 (T-helper) and Th2 cells mainly act
- Mainly act by activating other cells
Effects of IFN-gamma and CD40 ligands(produced by Th1 cells)
- Activates macrophage to destroy engulfed bacteria
Effects of fox ligand or LT-alpha (produced by TH1)
- Kills chronically infected cells, releasing bacteria to be destroyed by fresh macrophages
Effects of IL-2 (produced by Th1)
- Induces T-cell proliferation, increasing numbers of effector cells
Effects of IL-3 + GM-CSF
- Induces macrophage differentiation in the bone marrow
Effects of TNF-alpha + LT-beta
- Activates endothelium to induce macrophage binding and exit from blood vessel at site of infection
What is X-linked SCID (severe combined immunodeficiency) caused by
- Is caused by the genetic inactivation (by mutation) of one receptor that is a common signalling component of the IL-2, IL-4 and IL-7 receptors
How was the inflammatory role of cytokines discovered
- Was discovered by studying the immunopathogenesis of cachexia during infection
- It was found that activated macrophages produce an inflammatory mediator (cytokine) that, among other things, induced cachexia
- When they had its sequence, they found it was identical to TNF
Cardinal signs of inflammation
- Heat
- Swelling
- Redness
- Pain
- Tissue damage
Examples of TNF-mediated diseases
- Septic shock
- Multiple organ failure
- Respiratory distress syndrome
- Rheumatoid arthritis
- Inflammatory bowel disease
- Graft-versus-host rejection
- Diabetes
- Pulmonary fibrosis
Cytokines in allergy
- While Th1 cytokines are important in inflammatory diseases, Th2 cytokines are important in allergic diseases
What is Th1/Th2 differentiation viewed as a balance between
- Inflammation/Asthma
- Inflammatory/anti-inflammatory
T cell subsets - Naive CD4
Th1 - IFN-gamma - inflammation
Th2 - IL-4,5,9 and 13 - allergy, anti-inflammation
Th17 - IL-17 - inflammation
Treg - IL-10, inhibit activity of other T cells - anti-inflammation
What is MCP-1/CCL2
The chemokine (C-C motif) ligand 2 (CCL2) is also referred to as monocyte chemoattractant protein 1 (MCP1) - is a chemokine
CCL2 recruits monocytes, memory T cells, and dendritic cells to the sites of inflammation produced by either tissue injury or infection
Therapeutic use of IFN-gamma
- Macrophage activation
Therapeutic use of IFN-beta
- ‘Immunomodulation’
Therapeutic use of IL-2
Host defense - Melanoma, renal cell carcinoma
Therapeutic use of IFN-alpha
Host defense - Hairy cell leukemia, kaposi, viral hepatitis
Therapeutic use of GM-CSF
Hemopoiesis
- Myeloreconstitution following bone marrow transplant, chemotherapy-induced neutropenia
Therapeutic use of G-CSF
Hemopoiesis
- Chemotherapy-induced neutropenia
Therapeutic use of IL-11
Hemopoiesis
- Thrombocytopenia in oncology
Therapeutic use of EPO
Hemopoiesis
- Anaemia
Therapeutic use of anti-tNF and sTNFR
- Rheumatoid arthritis, crohn’s, ulcerative colitis, psoriasis
Therapeutic use of IL-1Ra
- Rheumatoid arthritis, cryopyrin-associated periodic syndromes, CAPS
Therapeutic use of anti-IL-6, IL-6R
- Rheumatoid arthritis
Therapeutic use of anti-IL-17,-12,-23
- Psoriasis, psoriatic arthritis, ankylosing spondylitis, crohn
Therapeutic use of anti-IL-5
- Reslizumab, mepolizumab; approved FDA 2016-2017 for asthma and eosinophilic granulomatosis
Therapeutic use of anti-IL-4R
- Dupilumab; approved FDA 2017 for atopic dermatitis (eczema)
Examples of cytokine inhibitors
- Antibodies anti-cytokine or their soluble receptors (to mop them up); antibodies to their receptor (to block their binding site)
What is ustekinumab
- Is an antibody directed against the p40 subunit of IL-12 and IL-23, so it inhibits both
- Approved for psoriasis and crohn’s disease
What does pleiotropic mean
- Acts on many different targets (has many actions)
Consequences of pleiotrophic effects
- The success and effectiveness of anti-TNF therapy (and other anti-cytokine drugs) in chronic inflammatory diseases should not let us forget their role in innate immunity
- Side effects of anti-TNF, anti-IL-17, anti-IL-6 include increased susceptibility to TB and serious opportunistic infections, including listeria, pneumocytosis and others
Example of pleiotrophic medication and its side effects
- Enbrel
- Serious infections including sepsis and TB have been reported
- TB (including disseminated or extrapulmonary presentation) has been observed in patients receiving TNF-blocking agents such as enbrel
- TB may be due to reactivation of latent TB infection or to new infection
- Reactivation of hep B and worsening of hep C